Windows 2000

Windows 2000 is a business-oriented operating system that was produced by Microsoft and was released as part of the Windows NT family of operating systems. It was succeeded by Windows XP in 2001, releasing to manufacturing on December 15, 1999 and being officially released to retail on February 17, 2000. It is the successor to Windows NT 4.0.
Four editions of Windows 2000 were released: "Professional", "Server", "Advanced Server", and "Datacenter Server"; the latter was both released to manufacturing and launched months after the other editions. While each edition of Windows 2000 was targeted at a different market, they shared a core set of features, including many system utilities such as the Microsoft Management Console and standard system administration applications.
Windows 2000 introduces NTFS 3.0, Encrypting File System, as well as basic and dynamic disk storage. Support for people with disabilities was improved over Windows NT 4.0 with a number of new assistive technologies, and Microsoft increased support for different languages and locale information. The Windows 2000 Server family has additional features, most notably the introduction of Active Directory, which in the years following became a widely used directory service in business environments.
Microsoft marketed Windows 2000 as the most secure Windows version ever at the time; however, it became the target of a number of high-profile virus attacks such as Code Red and Nimda. For ten years after its release, it continued to receive patches for security vulnerabilities nearly every month until reaching the end of its lifecycle on July 13, 2010.
Windows NT 5.0 is the last version of Microsoft Windows to display the "Windows NT" designation. Windows 2000 and Windows 2000 Server are succeeded by Windows XP (released in October 2001) and Windows Server 2003 (released in April 2003), respectively.
History.
Windows 2000 is a continuation of the Microsoft Windows NT family of operating systems, replacing Windows NT 4.0. The original name for the operating system was Windows NT 5.0 and the first beta was released in September 1997, followed by Beta 2 in August 1998. On October 27, 1998, Microsoft announced that the name of the final version of the operating system would be Windows 2000, a name which referred to its projected release date. Windows 2000 Beta 3 was released in May 1999. NT 5.0 Beta 1 was similar to NT 4.0, including a very similarly themed logo. NT 5.0 Beta 2 introduced a new 'mini' boot screen, and removed the 'dark space' theme in the logo. The NT 5.0 betas had very long startup and shutdown sounds, though these were changed in the early Windows 2000 beta, but during Beta 3, a new piano-made startup and shutdown sounds were made, featured in the final version as well as in Windows Me. The new login prompt from the final version made its first appearance in Beta 3 build 1946 (the first build of Beta 3). The new, updated icons (for "My Computer", "Recycle Bin" etc.) first appeared in Beta 3 build 1964. The Windows 2000 boot screen in the final version first appeared in Beta 3 build 1983. Windows 2000 did not have a codename because, according to Dave Thompson of Windows NT team, "Jim Allchin didn't like codenames".
Windows 2000 Service Pack 1 was codenamed "Asteroid" and Windows 2000 64-bit was codenamed "Janus." During development, there was a build for the Alpha which was abandoned some time after RC1 after Compaq announced they had dropped support for Windows NT on Alpha. From here, Microsoft issued three release candidates between July and November 1999, and finally released the operating system to partners on December 12, 1999. The public could buy the full version of Windows 2000 on February 17, 2000. Three days before this event, which Microsoft advertised as "a standard in reliability," a leaked memo from Microsoft reported on by Mary Jo Foley revealed that Windows 2000 had "over 63,000 potential known defects." After Foley's article was published, she claimed that Microsoft blacklisted her for a considerable time. However, Abraham Silberschatz et al. claim in their computer science textbook that "Windows 2000 was the most reliable, stable operating system Microsoft had ever shipped to that point. Much of this reliability came from maturity in the source code, extensive stress testing of the system, and automatic detection of many serious errors in drivers." InformationWeek summarized the release "our tests show the successor to NT 4.0 is everything we hoped it would be. Of course, it isn't perfect either." Wired News later described the results of the February launch as "lackluster." Novell criticized Microsoft's Active Directory, the new directory service architecture, as less scalable or reliable than its own Novell Directory Services (NDS) alternative.
Windows 2000 was initially planned to replace both Windows 98 and Windows NT 4.0. However, this changed later, as an updated version of Windows 98 called Windows 98 SE was released in 1999.
On or shortly before February 12, 2004, "portions of the Microsoft Windows 2000 and Windows NT 4.0 source code were illegally made available on the Internet." The source of the leak was later traced to Mainsoft, a Windows Interface Source Environment partner. Microsoft issued the following statement:
 "Microsoft source code is both copyrighted and protected as a trade secret. As such, it is illegal to post it, make it available to others, download it or use it."
Despite the warnings, the archive containing the leaked code spread widely on the file-sharing networks. On February 16, 2004, an exploit "allegedly discovered by an individual studying the leaked source code" for certain versions of Microsoft Internet Explorer was reported. On April 15, 2015, GitHub took down a repository containing a copy of the Windows NT 4.0 source code that originated from the leak.
Microsoft planned to release a 64-bit version of Windows 2000, which would run on 64-bit Intel Itanium microprocessors, in 2000. However, the first officially released 64-bit version of Windows was "Windows XP 64-Bit Edition", released alongside the 32-bit editions of Windows XP on October 25, 2001, followed by the server versions "Windows Datacenter Server Limited Edition" and later "Windows Advanced Server Limited Edition", which were based on the pre-release Windows Server 2003 (then known as "Windows .NET Server") codebase. These editions were released in 2002, were shortly available through the OEM channel and then were superseded by the final versions of Server 2003.
New and updated features.
Windows 2000 introduced many of the new features of Windows 98 and 98 SE into the NT line, such as the Windows Desktop Update, Internet Explorer 5 (Internet Explorer 6, which followed in 2001, is also available for Windows 2000), Outlook Express, NetMeeting, FAT32 support, Windows Driver Model, Internet Connection Sharing, Windows Media Player, WebDAV support etc. Certain new features are common across all editions of Windows 2000, among them NTFS 3.0, the Microsoft Management Console (MMC), UDF support, the Encrypting File System (EFS), Logical Disk Manager, Image Color Management 2.0, support for PostScript 3-based printers, OpenType codice_1 and Type 1 PostScript codice_2 font support (including a new font—Palatino Linotype—to showcase some OpenType features), the Data protection API (DPAPI), an LDAP/Active Directory-enabled Address Book, usability enhancements and multi-language and locale support. Windows 2000 also introduced USB device class drivers for USB printers, Mass storage class devices, and improved FireWire SBP-2 support for printers and scanners, along with a "Safe removal" applet for storage devices. Windows 2000 SP4 has added the native USB 2.0 support. Windows 2000 is also the first Windows version to support hibernation at the operating system level (OS-controlled ACPI S4 sleep state) unlike Windows 98 which required special drivers from the hardware manufacturer or driver developer.
A new capability designed to protect critical system files called Windows File Protection was introduced. This protects critical Windows system files by preventing programs other than Microsoft's operating system update mechanisms such as the "Package Installer", Windows Installer and other update components from modifying them. The System File Checker utility provides users the ability to perform a manual scan of the integrity of all protected system files, and optionally repair them, either by restoring from a cache stored in a separate "DLLCACHE" directory, or from the original install media.
Microsoft recognized that a serious error (a Blue Screen of Death or stop error) could cause problems for servers that needed to be constantly running and so provided a system setting that would allow the server to automatically reboot when a stop error occurred. Also included is an option to dump any of the first 64 KB of memory to disk (the smallest amount of memory that is useful for debugging purposes, also known as a minidump), a dump of only the kernel's memory, or a dump of the entire contents of memory to disk, as well as write that this event happened to the Windows 2000 event log. In order to improve performance on servers running Windows 2000, Microsoft gave administrators the choice of optimizing the operating system's memory and processor usage patterns for background services or for applications. Windows 2000 also introduced core system administration and management features as the Windows Installer, Windows Management Instrumentation and Event Tracing for Windows (ETW) into the operating system.
Plug and Play and hardware support improvements.
The most notable improvement from Windows NT 4.0 is the addition of Plug and Play with full ACPI and Windows Driver Model support. Similar to Windows 9x, Windows 2000 supports automatic recognition of installed hardware, hardware resource allocation, loading of appropriate drivers, PnP APIs and device notification events. The addition of the kernel PnP Manager along with the Power Manager are two significant subsystems added in Windows 2000.
Windows 2000 introduced version 3 print drivers (user mode printer drivers) based on Unidrv, which made it easier for printer manufacturers to write device drivers for printers. Generic support for 5-button mice is also included as standard and installing IntelliPoint allows reassigning the programmable buttons. Windows 98 lacked generic support. Driver Verifier was introduced to stress test and catch device driver bugs.
Shell.
Windows 2000 introduces layered windows that allow for transparency, translucency and various transition effects like shadows, gradient fills and alpha-blended GUI elements to top-level windows. Menus support a new "Fade" transition effect.
The Start menu in Windows 2000 introduces "personalized menus", expandable special folders and the ability to launch multiple programs without closing the menu by holding down the codice_3 key. A "Re-sort" button forces the entire Start Menu to be sorted by name. The Taskbar introduces support for balloon notifications which can also be used by application developers. Windows 2000 Explorer introduces customizable Windows Explorer toolbars, auto-complete in Windows Explorer address bar and Run box, advanced file type association features, displaying comments in shortcuts as tooltips, extensible columns in Details view (IColumnProvider interface), icon overlays, integrated search pane in Windows Explorer, sort by name function for menus, and "Places bar" in common dialogs for "Open" and "Save".
Windows Explorer has been enhanced in several ways in Windows 2000. It is the first Windows NT release to include Active Desktop, first introduced as a part of Internet Explorer 4.0 (specifically Windows Desktop Update), and only pre-installed in Windows 98 by that time. It allowed users to customize the way folders look and behave by using HTML templates, having the file extension codice_4. This feature was abused by computer viruses that employed malicious scripts, Java applets, or ActiveX controls in folder template files as their infection vector. Two such viruses are VBS/Roor-C<ref name="VBS/Roor-C">"Sophos", VBS/Roor-C threat analysis . Retrieved August 26, 2007.</ref> and VBS.Redlof.a.
The "Web-style" folders view, with the left Explorer pane displaying details for the object currently selected, is turned on by default in Windows 2000. For certain file types, such as pictures and media files, the preview is also displayed in the left pane. Until the dedicated interactive preview pane appeared in Windows Vista, Windows 2000 had been the only Windows release to feature an interactive media player as the previewer for sound and video files, enabled by default. However, such a previewer can be enabled in previous versions of Windows with the Windows Desktop Update installed through the use of folder customization templates. The default file tooltip displays file title, author, subject and comments; this metadata may be read from a special NTFS stream, if the file is on an NTFS volume, or from an OLE structured storage stream, if the file is a structured storage document. All Microsoft Office documents since Office 4.0 make use of structured storage, so their metadata is displayable in the Windows 2000 Explorer default tooltip. File shortcuts can also store comments which are displayed as a tooltip when the mouse hovers over the shortcut. The shell introduces extensibility support through metadata handlers, icon overlay handlers and column handlers in Explorer "Details view".
The right pane of Windows 2000 Explorer, which usually just lists files and folders, can also be customized. For example, the contents of the system folders aren't displayed by default, instead showing in the right pane a warning to the user that modifying the contents of the system folders could harm their computer. It's possible to define additional Explorer panes by using DIV elements in folder template files. This degree of customizability is new to Windows 2000; neither Windows 98 nor the Desktop Update could provide it. The new DHTML-based search pane is integrated into Windows 2000 Explorer, unlike the separate search dialog found in all previous Explorer versions. The Indexing Service has also been integrated into the operating system and the search pane built into Explorer allows searching files indexed by its database.
NTFS 3.0.
Microsoft released the version 3.0 of NTFS (sometimes incorrectly called "NTFS 5" in relation to the kernel version number) as part of Windows 2000; this introduced disk quotas (provided by QuotaAdvisor), file-system-level encryption, sparse files and reparse points. Sparse files allow for the efficient storage of data sets that are very large yet contain many areas that only have zeros. Reparse points allow the object manager to reset a file namespace lookup and let file system drivers implement changed functionality in a transparent manner. Reparse points are used to implement volume mount points, junctions, Hierarchical Storage Management, Native Structured Storage and Single Instance Storage. Volume mount points and directory junctions allow for a file to be transparently referred from one file or directory location to another.
Windows 2000 also introduces a "Distributed Link Tracking" service to ensure file shortcuts remain working even if the target is moved or renamed. The target object's unique identifier is stored in the shortcut file on NTFS 3.0 and Windows can use the Distributed Link Tracking service for tracking the targets of shortcuts, so that the shortcut file may be silently updated if the target moves, even to another hard drive.
Encrypting File System.
The Encrypting File System (EFS) introduced strong file system-level encryption to Windows. It allows any folder or drive on an NTFS volume to be encrypted transparently by the user. EFS works together with the EFS service, Microsoft's CryptoAPI and the EFS File System Runtime Library (FSRTL). To date, its encryption has not been compromised.
EFS works by encrypting a file with a bulk symmetric key (also known as the File Encryption Key, or FEK), which is used because it takes less time to encrypt and decrypt large amounts of data than if an asymmetric key cipher were used. The symmetric key used to encrypt the file is then encrypted with a public key associated with the user who encrypted the file, and this encrypted data is stored in the header of the encrypted file. To decrypt the file, the file system uses the private key of the user to decrypt the symmetric key stored in the file header. It then uses the symmetric key to decrypt the file. Because this is done at the file system level, it is transparent to the user.
For a user losing access to their key, support for recovery agents that can decrypt files is built into EFS. A Recovery Agent is a user who is authorized by a public key recovery certificate to decrypt files belonging to other users using a special "private key". By default, local administrators are "recovery agents" however they can be customized using Group Policy.
Basic and dynamic disk storage.
Windows 2000 introduced the Logical Disk Manager and the diskpart command line tool for dynamic storage. All versions of Windows 2000 support three types of dynamic disk volumes (along with basic disks): "simple volumes", "spanned volumes" and "striped volumes":
In addition to these disk volumes, Windows 2000 Server, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server support "mirrored volumes" and "striped volumes with parity":
Accessibility.
With Windows 2000, Microsoft introduced the Windows 9x accessibility features for people with visual and auditory impairments and other disabilities into the NT-line of operating systems. These included:
Additionally, Windows 2000 introduced the following new accessibility features:
Languages and locales.
Windows 2000 introduced the Multilingual User Interface (MUI). Besides English, Windows 2000 incorporates support for Arabic, Armenian, Baltic, Central European, Cyrillic, Georgian, Greek, Hebrew, Indic, Japanese, Korean, Simplified Chinese, Thai, Traditional Chinese, Turkic, Vietnamese and Western European languages. It also has support for many different locales.
Games.
Windows 2000 included version 7.0 of the DirectX API, commonly used by game developers on Windows 98. The last version of DirectX that was released for Windows 2000 was DirectX 9.0c (Shader Model 3.0), which shipped with Windows XP Service Pack 2. Microsoft published quarterly updates to DirectX 9.0c through the February 2010 release after which support was dropped in the June 2010 SDK. These updates contain bug fixes to the core runtime and some additional libraries such as D3DX, XAudio 2, XInput and Managed DirectX components. The majority of games written for versions of DirectX 9.0c (up to the February 2010 release) can therefore run on Windows 2000.
Windows 2000 included the same games as Windows NT 4.0 did: FreeCell, Minesweeper, Pinball, and Solitaire.
System utilities.
Windows 2000 introduced the Microsoft Management Console (MMC), which is used to create, save, and open administrative tools. Each of these is called a "console", and most allow an administrator to administer other Windows 2000 computers from one centralised computer. Each console can contain one or many specific administrative tools, called "snap-ins". These can be either standalone (with one function), or an extension (adding functions to an existing snap-in). In order to provide the ability to control what snap-ins can be seen in a console, the MMC allows consoles to be created in "author mode" or "user mode". Author mode allows snap-ins to be added, new windows to be created, all portions of the console tree to be displayed and consoles to be saved. User mode allows consoles to be distributed with restrictions applied. User mode consoles can grant full access to the user for any change, or they can grant limited access, preventing users from adding snapins to the console though they can view multiple windows in a console. Alternatively users can be granted limited access, preventing them from adding to the console and stopping them from viewing multiple windows in a single console.
The main tools that come with Windows 2000 can be found in the "Computer Management" console (in Administrative Tools in the Control Panel). This contains the Event Viewer—a means of seeing events and the Windows equivalent of a log file, a system information utility, a backup utility, Task Scheduler and management consoles to view open shared folders and shared folder sessions, configure and manage COM+ applications, configure Group Policy, manage all the local users and user groups, and a device manager. It contains "Disk Management" and "Removable Storage" snap-ins, a disk defragmenter as well as a performance diagnostic console, which displays graphs of system performance and configures data logs and alerts. It also contains a service configuration console, which allows users to view all installed services and to stop and start them, as well as configure what those services should do when the computer starts. CHKDSK has significant performance improvements.
Windows 2000 comes with two utilities to edit the Windows registry, "REGEDIT.EXE" and "REGEDT32.EXE". REGEDIT has been directly ported from Windows 98, and therefore does not support editing registry permissions. REGEDT32 has the older multiple document interface (MDI) and can edit registry permissions in the same manner that Windows NT's REGEDT32 program could. REGEDIT has a left-side tree view of the Windows registry, lists all loaded hives and represents the three components of a value (its name, type, and data) as separate columns of a table. REGEDT32 has a left-side tree view, but each hive has its own window, so the tree displays only keys and it represents values as a list of strings. REGEDIT supports right-clicking of entries in a tree view to adjust properties and other settings. REGEDT32 requires all actions to be performed from the top menu bar. Windows XP is the first system to integrate these two programs into a single utility, adopting the REGEDIT behavior with the additional NT features.
The System File Checker (SFC) also comes with Windows 2000. It is a command line utility that scans system files and verifies whether they were signed by Microsoft and works in conjunction with the Windows File Protection mechanism. It can also repopulate and repair all the files in the "Dllcache" folder.
Recovery Console.
The Recovery Console is run from outside the installed copy of Windows to perform maintenance tasks that can neither be run from within it nor feasibly be run from another computer or copy of Windows 2000. It is usually used to recover the system from problems that cause booting to fail, which would render other tools useless, like Safe Mode or Last Known Good Configuration, or codice_11. It includes commands like codice_12, which are not present in MS-DOS.
It has a simple command-line interface, used to check and repair the hard drive(s), repair boot information (including NTLDR), replace corrupted system files with fresh copies from the CD, or enable/disable services and drivers for the next boot.
The console can be accessed in either of the two ways:
Windows Scripting Host 2.0.
Windows 2000 introduced Windows Script Host 2.0 which included an expanded object model and support for logon and logoff scripts.
Server family features.
The Windows 2000 Server family consists of Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Small Business Server, and Windows 2000 Datacenter Server.
All editions of Windows 2000 Server have the following services and features built in:
The Server editions include more features and components, including the Microsoft Distributed File System (DFS), Active Directory support and fault-tolerant storage.
Distributed File System.
The Distributed File System (DFS) allows shares in multiple different locations to be logically grouped under one folder, or "DFS root". When users try to access a network share off the DFS root, the user is really looking at a "DFS link" and the DFS server transparently redirects them to the correct file server and share. A DFS root can only exist on a Windows 2000 version that is part of the server family, and only one DFS root can exist on that server.
There can be two ways of implementing a DFS namespace on Windows 2000: either through a standalone DFS root or a domain-based DFS root. Standalone DFS allows for only DFS roots on the local computer, and thus does not use Active Directory. Domain-based DFS roots exist within Active Directory and can have their information distributed to other domain controllers within the domain – this provides fault tolerance to DFS. DFS roots that exist on a domain must be hosted on a domain controller or on a domain member server. The file and root information is replicated via the Microsoft File Replication Service (FRS).
Active Directory.
A new way of organizing Windows network domains, or groups of resources, called Active Directory, is introduced with Windows 2000 to replace Windows NT's earlier domain model. Active Directory's hierarchical nature allowed administrators a built-in way to manage user and computer policies and user accounts, and to automatically deploy programs and updates with a greater degree of scalability and centralization than provided in previous Windows versions. User information stored in Active Directory also provided a convenient phone book-like function to end users. Active Directory domains can vary from small installations with a few hundred objects, to large installations with millions. Active Directory can organise and link groups of domains into a contiguous domain name space to form "trees". Groups of trees outside of the same namespace can be linked together to form "forests."
Active Directory services could always be installed on a Windows 2000 Server Standard, Advanced, or Datacenter computer, and cannot be installed on a Windows 2000 Professional computer. However, Windows 2000 Professional is the first client operating system able to exploit Active Directory's new features. As part of an organization's migration, Windows NT clients continued to function until all clients were upgraded to Windows 2000 Professional, at which point the Active Directory domain could be switched to native mode and maximum functionality achieved.
Active Directory requires a DNS server that supports SRV resource records, or that an organization's existing DNS infrastructure be upgraded to support this. There should be one or more domain controllers to hold the Active Directory database and provide Active Directory directory services.
Volume fault tolerance.
Along with support for simple, spanned and striped volumes, the Windows 2000 Server family also supports fault-tolerant volume types. The types supported are "mirrored volumes" and "RAID-5 volumes":
Deployment.
Windows 2000 can be deployed to a site via various methods. It can be installed onto servers via traditional media (such as CD) or via distribution folders that reside on a shared folder. Installations can be attended or unattended. During a manual installation, the administrator must specify configuration options. Unattended installations are scripted via an answer file, or a predefined script in the form of an INI file that has all the options filled in. An answer file can be created manually or using the graphical "Setup manager". The Winnt.exe or Winnt32.exe program then uses that answer file to automate the installation. Unattended installations can be performed via a bootable CD, using Microsoft Systems Management Server (SMS), via the System Preparation Tool (Sysprep), via the Winnt32.exe program using the /syspart switch or via Remote Installation Services (RIS). The ability to slipstream a service pack into the original operating system setup files is also introduced in Windows 2000.
The Sysprep method is started on a standardized reference computer – though the hardware need not be similar – and it copies the required installation files from the reference computer to the target computers. The hard drive does not need to be in the target computer and may be swapped out to it at any time, with the hardware configured later. The Winnt.exe program must also be passed a /unattend switch that points to a valid answer file and a /s file that points to one or more valid installation sources.
Sysprep allows the duplication of a disk image on an existing Windows 2000 Server installation to multiple servers. This means that all applications and system configuration settings will be copied across to the new installations, and thus, the reference and target computers must have the same HALs, ACPI support, and mass storage devices – though Windows 2000 automatically detects "plug and play" devices. The primary reason for using Sysprep is to quickly deploy Windows 2000 to a site that has multiple computers with standard hardware. (If a system had different HALs, mass storage devices or ACPI support, then multiple images would need to be maintained.)
Systems Management Server can be used to upgrade multiple computers to Windows 2000. These must be running Windows NT 3.51, Windows NT 4.0, Windows 98 or Windows 95 OSR2.x along with the SMS client agent that can receive software installation operations. Using SMS allows installations over a wide area and provides centralised control over upgrades to systems.
Remote Installation Services (RIS) are a means to automatically install Windows 2000 Professional (and not Windows 2000 Server) to a local computer over a network from a central server. Images do not have to support specific hardware configurations and the security settings can be configured after the computer reboots as the service generates a new unique security ID (SID) for the machine. This is required so that local accounts are given the right identifier and do not clash with other Windows 2000 Professional computers on a network.
RIS requires that client computers are able to boot over the network via either a network interface card that has a Pre-Boot Execution Environment (PXE) boot ROM installed or that the client computer has a network card installed that is supported by the remote boot disk generator. The remote computer must also meet the Net PC specification. The server that RIS runs on must be Windows 2000 Server and it must be able to access a network DNS Service, a DHCP service and the Active Directory services.
Editions.
Microsoft released various editions of Windows 2000 for different markets and business needs: Professional, Server, Advanced Server and Datacenter Server. Each was packaged separately.
Windows 2000 Professional was designed as the desktop operating system for businesses and power users. It is the client version of Windows 2000. It offers greater security and stability than many of the previous Windows desktop operating systems. It supports up to two processors, and can address up to 4GB of RAM. The system requirements are a Pentium processor (or equivalent) of 133MHz or greater, at least 32MB of RAM, 650MB of hard drive space, and a CD-ROM drive (recommended: Pentium II, 128MB of RAM, 2GB of hard drive space, and CD-ROM drive).
Windows 2000 Server shares the same user interface with Windows 2000 Professional, but contains additional components for the computer to perform server roles and run infrastructure and application software. A significant new component introduced in the server versions is Active Directory, which is an enterprise-wide directory service based on LDAP (Lightweight Directory Access Protocol). Additionally, Microsoft integrated Kerberos network authentication, replacing the often-criticised NTLM (NT LAN Manager) authentication system used in previous versions. This also provided a purely transitive-trust relationship between Windows 2000 Server domains in a "forest" (a collection of one or more Windows 2000 domains that share a common schema, configuration, and global catalog, being linked with two-way transitive trusts). Furthermore, Windows 2000 introduced a Domain Name Server which allows dynamic registration of IP addresses. Windows 2000 Server supports up to 4 processors and 4GB of RAM, with a minimum requirement of 128MB of RAM and 1GB hard disk space, however requirements may be higher depending on installed components.
Windows 2000 Advanced Server is a variant of Windows 2000 Server operating system designed for medium-to-large businesses. It offers the ability to create clusters of servers, support for up to 8 CPUs, a main memory amount of up to 8GB on Physical Address Extension (PAE) systems and the ability to do 8-way SMP. It supports TCP/IP load balancing and builds on Microsoft Cluster Server (MSCS) in Windows NT Enterprise Server 4.0, adding enhanced functionality for two-node clusters. System requirements are similar to those of Windows 2000 Server, however they may need to be higher to scale to larger infrastructure.
Windows 2000 Datacenter Server is a variant of Windows 2000 Server designed for large businesses that move large quantities of confidential or sensitive data frequently via a central server. Like Advanced Server, it supports clustering, failover and load balancing. Its minimum system requirements are normal, but it was designed to be capable of handing advanced, fault-tolerant and scalable hardware—for instance computers with up to 32 CPUs and 32GBs RAM, with rigorous system testing and qualification, hardware partitioning, coordinated maintenance and change control. System requirements are similar to those of Windows 2000 Server Advanced, however they may need to be higher to scale to larger infrastructure. Windows 2000 Datacenter Server was released to manufacturing on August 11, 2000 and launched on September 26, 2000. This edition was based on Windows 2000 with Service Pack 1 and was not available at retail.
Service packs.
Windows 2000 has received four full service packs and one rollup update package following SP4, which is the last service pack. Microsoft phased out all development of its Java Virtual Machine (JVM) from Windows 2000 in SP3. Internet Explorer 5.01 has also been upgraded to the corresponding service pack level.
Microsoft had originally intended to release a fifth service pack for Windows 2000, but Microsoft cancelled this project early in its development, and instead released Update Rollup 1 for SP4, a collection of all the security-related hotfixes and some other significant issues. The Update Rollup does not include all non-security related hotfixes and is not subjected to the same extensive regression testing as a full service pack. Microsoft states that this update will meet customers' needs better than a whole new service pack, and will still help Windows 2000 customers secure their PCs, reduce support costs, and support existing computer hardware.
Upgradeability.
Several Windows 2000 components are upgradable to latest versions, which include new versions introduced in later versions of Windows, and other major Microsoft applications are available. These latest versions for Windows 2000 include:
Security.
During the Windows 2000 period, the nature of attacks on Windows servers changed: more attacks came from remote sources via the Internet. This has led to an overwhelming number of malicious programs exploiting the IIS services – specifically a notorious buffer overflow tendency. This tendency is not operating-system-version specific, but rather configuration-specific: it depends on the services that are enabled. Following this, a common complaint is that "by default, Windows 2000 installations contain numerous potential security problems. Many unneeded services are installed and enabled, and there is no active local security policy." In addition to insecure defaults, according to the SANS Institute, the most common flaws discovered are remotely exploitable buffer overflow vulnerabilities. Other criticized flaws include the use of vulnerable encryption techniques.
Code Red and Code Red II were famous (and much discussed) worms that exploited vulnerabilities of the Windows Indexing Service of Windows 2000's Internet Information Services (IIS). In August 2003, security researchers estimated that two major worms called Sobig and Blaster infected more than half a million Microsoft Windows computers. The 2005 Zotob worm was blamed for security compromises on Windows 2000 machines at ABC, CNN, the New York Times Company, and the United States Department of Homeland Security.
On September 8, 2009, Microsoft skipped patching two of the five security flaws that were addressed in the monthly security update, saying that patching one of the critical security flaws was "infeasible." According to Microsoft Security Bulletin MS09-048: "The architecture to properly support TCP/IP protection does not exist on Microsoft Windows 2000 systems, making it infeasible to build the fix for Microsoft Windows 2000 Service Pack 4 to eliminate the vulnerability. To do so would require re-architecting a very significant amount of the Microsoft Windows 2000 Service Pack 4 operating system, there would be no assurance that applications designed to run on Microsoft Windows 2000 Service Pack 4 would continue to operate on the updated system." No patches for this flaw were released for the newer Windows XP (32-bit) and Windows XP Professional x64 Edition either, despite both also being affected; Microsoft suggested turning on Windows Firewall in those versions.
Support lifecycle.
Windows 2000 and Windows 2000 Server were superseded by newer Microsoft operating systems: Windows 2000 Server products by Windows Server 2003, and Windows 2000 Professional by Windows XP Professional.
The Windows 2000 family of operating systems moved from mainstream support to the extended support phase on June 30, 2005. Microsoft says that this marks the progression of Windows 2000 through the Windows lifecycle policy. Under mainstream support, Microsoft freely provides design changes if any, service packs and non-security related updates in addition to security updates, whereas in extended support, service packs are not provided and non-security updates require contacting the support personnel by e-mail or phone. Under the extended support phase, Microsoft continued to provide critical security updates every month for all components of Windows 2000 (including Internet Explorer 5.0 SP4) and paid per-incident support for technical issues. Because of Windows 2000's age, updated versions of components such as Windows Media Player 11 and Internet Explorer 7 have not been released for it. In the case of Internet Explorer, Microsoft said in 2005 that, "some of the security work in IE 7 relies on operating system functionality in XP SP2 that is non-trivial to port back to Windows 2000."
While users of Windows 2000 Professional and Server were eligible to purchase the upgrade license for Windows Vista Business or Windows Server 2008, neither of these operating systems can directly perform an upgrade installation from Windows 2000; a clean installation must be performed instead or a two-step upgrade through XP/2003. Microsoft has dropped the upgrade path from Windows 2000 (and earlier) to Windows 7. Users of Windows 2000 must buy a full Windows 7 license.
Although Windows 2000 is the last NT-based version of Microsoft Windows which does not include product activation, Microsoft has introduced Windows Genuine Advantage for certain downloads and non-critical updates from the Download Center for Windows 2000.
Windows 2000 reached the end of its lifecycle on July 13, 2010 (alongside Service Pack 2 of Windows XP). It will not receive new security updates and new security-related hotfixes after this date. In Japan, over 130,000 servers and 500,000 PCs in local governments were affected; many local governments said that they will not update as they do not have funds to cover a replacement.
As of 2011, Windows Update still supports the Windows 2000 updates available on Patch Tuesday in July 2010, e.g., if older optional Windows 2000 features are enabled later. Microsoft Office products under Windows 2000 have their own product lifecycles. While Internet Explorer 6 for Windows XP did receive security patches up until it lost support, this is not the case for IE6 under Windows 2000. The Windows Malicious Software Removal Tool installed monthly by Windows Update for XP and later versions can be still downloaded manually for Windows 2000.
Microsoft in 2020 announced that it would disable the Windows Update service for SHA-1 endpoints and since Windows 2000 did not get an update for SHA-2, Windows Update Services are no longer available on the OS as of late July 2020. However as of April 2021, the old updates for Windows 2000 are still available on the Microsoft Update Catalog.
Total cost of ownership.
In October 2002, Microsoft commissioned IDC to determine the total cost of ownership (TCO) for enterprise applications on Windows 2000 versus the TCO of the same applications on Linux. IDC's report is based on telephone interviews of IT executives and managers of 104 North American companies in which they determined what they were using for a specific workload for file, print, security and networking services.
IDC determined that the four areas where Windows 2000 had a better TCO than Linux – over a period of five years for an average organization of 100 employees – were file, print, network infrastructure and security infrastructure. They determined, however, that Linux had a better TCO than Windows 2000 for web serving. The report also found that the greatest cost was not in the procurement of software and hardware, but in staffing costs and downtime. While the report applied a 40% productivity factor during IT infrastructure downtime, recognizing that employees are not entirely unproductive, it did not consider the impact of downtime on the profitability of the business. The report stated that Linux servers had less unplanned downtime than Windows 2000 servers. It found that most Linux servers ran less workload per server than Windows 2000 servers and also that none of the businesses interviewed used 4-way SMP Linux computers. The report also did not take into account specific application servers – servers that need low maintenance and are provided by a specific vendor. The report did emphasize that TCO was only one factor in considering whether to use a particular IT platform, and also noted that as management and server software improved and became better packaged the overall picture shown could change.


SYSTEM.DAT


Think Blue Linux

Think Blue Linux (sometimes "ThinkBlue Linux") was a port of Linux to IBM S/390 (later, zSeries) mainframe computers, done by the Millenux subsidiary of German company Thinking Objects Software GmbH.
The distribution consisted primarily of a collection of Red Hat Linux 6.1 packages (or RPMs) on top of IBM's port of the Linux kernel. Distribution of the product is scheduled to cease in early 2006, as most of its packages are out of date, and other Linux distributions support IBM mainframes. Most modern Linux distributions support IBM mainframes, making a special dedicated distribution unnecessary.


SIO (software)

SIO is a serial port driver package for OS/2 written by Raymond L. Gwinn. It is designed to not only improve performance over OS/2's default serial drivers, but also improve compatibility. SIO contains a virtualized FOSSIL (VX00) driver that can be loaded to provide FOSSIL support to DOS based communications software. SIO later added the ability to create virtualized COM ports, which, combined with the included program VMODEM, allows incoming telnet connections to be directed toward the virtualized COM port. Older communications software are also able to "call out" to telnet sites. This is possible due to a custom set of "AT" commands that allow users to pass a hostname to the VMODEM software.
SIO (and the included VMODEM software) became very popular among Bulletin Board System operators due to the incoming telnet feature, as well as drastic speed improvements over other telnet solutions of the time.


IBM 4860


CDOS.SYS


NEC V40


Caanoo

The GP2X Caanoo, more commonly known as Caanoo, stylized CAANOO, is an open source, Linux-based handheld video game console and portable media player developed by the South Korean company GamePark Holdings. It was released on August 16, 2010 in South Korea and were also sold throughout Europe. It is the successor to the GP2X Wiz, and was showcased at the Electronic Entertainment Expo 2010. The device's launch price was about US$150, which didn't reach any retail stores in North America.
The Caanoo is not a direct competitor of handheld consoles like Nintendo DS or PlayStation Portable, but rather an alternative open source device. Because of that, any software that is compatible can be run without the need of creating custom firmware or other homebrew applications. This is the last open-source gaming device by GamePark Holdings, as they ceased production and development of gaming hardware to focus solely on software.
Hardware.
Specifications.
NB: the CPU embedded on Pollux has a good tolerance to overclocking (until 750 MHz the system shouldn't have problems, just a shorter battery autonomy.)
Not all CPU/SoC are created equal and these results are theoretical. Some may not be able to push much past stock frequency. Overclocking will vary between each Caanoo.
Games/Applications.
The Caanoo can run several applications that emulate consoles or computer systems, such as DrPocketSnes for the Super NES, GnGEO for the Neo-Geo, Hu-Go for the PC Engine, PCSX ReArmed for original PlayStation games, MAME4all for arcade games and Picodrive for the Mega Drive/Genesis and its add-ons, as well as freeware homebrew games/applications. These applications are created by the community itself and not by the manufacturers. Most, if not all of this software can be found at OpenHandhelds, a community-driven website.
Gamepark Holdings also had a website focused on downloadable content named FunGP. It sold commercial Caanoo and Wiz games, as well as some retro Arcade games. It has since ceased operations.
Caanoo is not compatible with software built for previous GPH devices (such as the GP2X Wiz) without an application to allow it to do so. A compatibility layer named Ginge allows for most software to be compatible, and most applications have already been ported.
Multimedia capability.
The Caanoo is a video player, an audio player, photo viewer and E-Book reader.
External TV output.
The SoC Pollux embeds (besides to the primary LCD controller) an NTSC/PAL encoder with internal DAC to manage an external analog video signal (CVBS output: 720×480 or 720×576 pixel interlaced, respectively 60/50 Hz vertical sync and 15 kHz horizontal sync).


Nokia N75

The Nokia N75 is a smartphone by Nokia. It uses Series 60 3rd Edition of Symbian OS. AT&T Mobility is a carrier of the N75 in the United States. It has been made specifically for the North American 3G market, supporting WCDMA 850/1900 frequencies; however, it was also available in other countries such as the UK.
Reaction.
CNet gave it 3/5, liking the call quality and display but disliking the battery life and camera. Mobile Tech Review gave it 4/5. PCMag gave it 2.5/5 with similar praise and criticism.


Bcache

Bcache (abbreviated from "block cache") is a cache in the Linux kernel's block layer, which is used for accessing secondary storage devices. It allows one or more fast storage devices, such as flash-based solid-state drives (SSDs), to act as a cache for one or more slower storage devices, such as hard disk drives (HDDs); this effectively creates hybrid volumes and provides performance improvements.
Designed around the nature and performance characteristics of SSDs, Bcache also minimizes write amplification by avoiding random writes and turning them into sequential writes instead. This merging of I/O operations is performed for both the cache and the primary storage, helping in extending the lifetime of flash-based devices used as caches, and in improving the performance of write-sensitive primary storages, such as RAID 5 sets.
Bcache is licensed under the GNU General Public License (GPL), and Kent Overstreet is its primary developer. Overstreet considers Bcache as a "prototype" for the development of Bcachefs, a filesystem with significant improvements.
Overview.
Using Bcache makes it possible to have SSDs as another level of indirection within the data storage access paths, resulting in improved overall performance by using fast flash-based SSDs as caches for slower mechanical hard disk drives (HDDs) with rotational magnetic media. That way, the gap between SSDs and HDDs can be bridged the costly speed of SSDs gets combined with the cheap storage capacity of traditional HDDs.
Caching is implemented by using SSDs for storing data associated with performed random reads and random writes, using near-zero seek times as the most prominent feature of SSDs. Sequential I/O is not cached, to avoid rapid SSD cache invalidation on such operations that are already suitable enough for HDDs; going around the cache for big sequential writes is known as the write-around policy. Not caching the sequential I/O also helps in extending the lifetime of SSDs used as caches. Write amplification is avoided by not performing random writes to SSDs; instead, all random writes to SSD caches are always combined into block-level writes, ending up with rewriting only the complete erase blocks on SSDs.
Both "write-back" and "write-through" (which is the default) policies are supported for caching write operations. In case of the write-back policy, written data is stored inside the SSD caches first, and propagated to the HDDs later in a batched way while performing seek-friendly operations making Bcache to act also as an I/O scheduler. For the write-through policy, which ensures that no write operation is marked as finished until the data requested to be written has reached both SSDs and HDDs, performance improvements are reduced by effectively performing only caching of the written data.
Write-back policy with batched writes to HDDs provides additional benefits to write-sensitive redundant array of independent disks (RAID) layouts such as RAID 5 and RAID 6, which perform actual write operations as atomic read-modify-write sequences. That way, performance penalties of small random writes are reduced or avoided for such RAID layouts, by grouping them together and performing as batched sequential writes.
Caching performed by Bcache operates at the block device level, making itself file system–agnostic as long as the file system provides an embedded universally unique identifier (UUID); this requirement is satisfied by virtually all standard Linux file systems, as well as by swap partitions. Sizes of the logical blocks used internally by Bcache as caching extents can go down to the size of a single HDD sector.
History.
Bcache was first announced by Kent Overstreet in July 2010, as a completely working Linux kernel module, though at its early beta stage. The development continued for almost two years, until May 2012, at which point Bcache reached its production-ready state.
It was merged into the Linux kernel mainline in kernel version 3.10, released on June 30, 2013. Overstreet has since been developing the file system Bcachefs, based on ideas first developed in Bcache that he said began "evolving ... into a full blown, general-purpose POSIX filesystem". He describes Bcache as a "prototype" for the ideas that became Bcachefs and intends Bcachefs to replace Bcache. He officially announced Bcachefs in 2015, and as of 2018 has been submitting it for consideration for inclusion in the mainline Linux kernel.
Features.
As of version 3.10 of the Linux kernel, the following features are provided by Bcache:
Improvements.
, the following new features are planned for the future releases of Bcache:


Samsung Wave II S8530

The Samsung Wave II S8530 (or "Samsung Wave II") is the Successor of Samsung Wave S8500 smartphone running the bada 1.2 operating system designed by Samsung, which was commercially released on October, 2010. The Wave is a slim touchscreen phone powered by Samsung's "Hummingbird" CPU (S5PC110), which includes 1 GHz ARM Cortex-8 CPU and a powerful built-in PowerVR SGX 540 graphics engine, "Super LCD" screen and 720p high-definition video capture capabilities. Shortage of Super AMOLED screens was one of the primary reasons for the release of this model.
Hardware features.
Design
The phone is made of mostly metal alloy and is measured at 10.9 mm thick. In terms of form factor, it is a slate style featuring 3 physical buttons on the front: call, reject/ shutdown, and main menu button.
Screen
The screen is a capacitive touchscreen Super LCD with an anti-smudge oleophobic coating on top of the scratch-resistant tempered-glass (Gorilla Glass Display) touch panel which has been shown to be capable of resisting extreme friction (scratch-resistant). The screen resolution is 800x480 WVGA.
Processor
The phone features a 1 GHz SoC, which internally contains an ARM Cortex A8 CPU core that is identical to the ARM Cortex CPU core used in Apple's A4 package on package SoC. The Phone graphics engine is SGX 540 which is said to be capable of generating 90 million triangles per second (same as the SoC used on the Samsung Galaxy S).
And 256MB+128MB RAM (same hardware as Samsung Wave S8500).
Camera
The phone features a 5 megapixel which supports 2592 x 1944 pixels, along with autofocus, LED flash, Geo-tagging, face, blink detection, image stabilization, touch focus,etc. Other than these features it has various shooting modes such as beauty shot, smile shot, continuous, panorama and vintage shot. As a camcorder it is able to shoot 720p HD recording (1280x720) at 30 FPS with flash. As well as this, it is also able to record slow motion video (320x240) at 120 FPS with flash.
Other features
Other feature includes A-GPS, 2 GB/8 GB of internal storage with a microSDHC slot for an additional 32 GB. It also has a magnetometer, a proximity sensor, an accelerometer, 5.1-channel surround sound Mobile Theater, music recognition, a fake call service, smart search, Social Hub and it is the first phone to support Bluetooth version 3.0.
In addition to Bluetooth 3.0, the phone also features Wi-Fi 802.11 b/g/n, HSDPA 3.2 Mbit/s and HSUPA 2 Mbit/s.
This phone is available with both European/Asia 3G bandings and the North American 3G bandings. Keep in mind that the North American 3G bandings version of the phone is a limited availability and is not available in the US.
Software features.
User interface
The phone is one of the few smartphone to feature the Samsung bada operating system platform. The UI is Samsung's own Touchwiz 3.0. Touchwiz 3.0, like the 2 predecessors (Touchwiz 2.0 and Touchwiz), utilises widgets. The 3 most notable widgets pre-installed in Touchwiz 3.0 are Daily Briefing (which includes all essential information such as weather, finance, AP mobile news and schedule), Feeds and Updates and Buddies now (which allows users to call, send texts to and read Facebook/Twitter feeds off their favourite contacts). Users are allowed to have up to 10 homescreens to add widgets.
Applications
In terms of Internet Browser, Samsung Wave is pre-installed with Dolphin Browser v2.0 (based on WebKit). While this browser supports Flash it is disabled by default to improve page load time.
By default, the phone comes with Picsel Viewer which is capable of reading .pdf and Microsoft Office file formats. Users from selected countries can buy and download Picsel Office Editor from Samsung Apps.
As for Samsung apps, users can also download applications, games and widgets from the application store.
Other software includes the GPS software that comes with this phone (LBS Route 66), Palringo IM, Facebook, Twitter, social hub, mini diary, daily briefing, memo, video player, FM radio, media browser, voice recorder, e-mail and pre-installed asphalt5.
Media support
MP3, AAC, AAC+, e-AAC+, WMA, AMR, WAV, MP4, FLAC, MPEG4, H.263, H.264, WMV, AVI, DivX, XviD, MKV
Android porting
Due to many owners of the phone disliking the Bada software many people have worked on porting the popular Android O.S to the Wave 2. The ported versions known are Froyo, Gingerbread, Ice Cream Sandwich, Jelly Bean and Kitkat. However they are still being developed and some features, such as GPS, may be limited or not function as intended.
External links.
Samsung site:
Reviews:
Support Forums


List of Nintendo 3DS colors and styles

This following is a list of case colors and styles that have been produced for the Nintendo 3DS family of handheld game consoles produced by Nintendo. Although the system initially launched with only two colors, its lineup has subsequently expanded to incorporate many more color varieties and limited editions, some of which are exclusive to various regions. As such, the list includes all color variations of regular Nintendo 3DS and New Nintendo 3DS, as well as their larger models, the Nintendo 3DS XL and New Nintendo 3DS XL along with the Chinese version, the iQue 3DS XL, and the entry-level versions, the Nintendo 2DS and New Nintendo 2DS XL.


XCOPY.EXE


Server Base System Architecture

The Server Base System Architecture (SBSA) is a hardware system architecture for servers based on 64-bit ARM processors.
Rationale.
Historically, ARM-based products have often been tailored for specific applications and power profiles. Variation between ARM-based hardware platforms has been an impediment requiring operating system adjustments for each product.
The SBSA seeks to strengthen the ARM ecosystem by specifying a minimal set of standardized features so that an OS built for this standard platform should function correctly without modification on all hardware products compliant with the specification.
Features.
Existing specifications for USB, PCIe, ACPI, TPM, and other standards are incorporated to solidify the specification.
Server Base Boot Requirements.
Firmware issues are addressed separately in the Server Base Boot Requirements (SBBR) specification.
Platform validation.
The Architecture Compliance Suite (ACS) checks whether an environment is compliant with the SBSA specification, and is provided under an Apache 2 open source license. It is available at https://github.com/ARM-software/sbsa-acs.
Compliance levels.
The specification defines levels of compliance, with level 0 being the most basic, and successive levels building on prior levels. In the words of the spec, "Unless explicitly stated, all specification items belonging to level N apply to levels greater than N."
Level 0, 1, and 2.
Levels 0, 1, and 2 have been deprecated and folded into level 3.
Level 3.
Level 3 contains base-level specifications for:
Level 4.
Extends level 3, e.g. with support for RAS fault recovery extensions of ARMv8.2 spec.
Level 5.
Extends level 4, e.g. with support for stage 2 translation control from hypervisor as specified in ARMv8.4.
Level 6.
Extends level 5, e.g. with support for speculative execution safety features.
Versions.
Initial public version.
Initial public version of the SBSA was announced on January 29, 2014.
SBSA Version 3.0.
SBSA Version 3.0 was released on February 1, 2016.
SBSA Version 5.0.
SBSA Version 5.0 was released on May 30, 2018.
SBSA Version 6.0.
SBSA Version 6.0 was released on September 16, 2019.


TYPE.COM


Abbey Silverstone

Abbey Silverstone is a very early member of the computer development family with a 50-year career in the computer industry that included time as Co-founder and VP of operations of Silicon Graphics (SGI).
Silverstone has a BS in Industrial Administration from the University of Illinois where, as a student, he worked with the IBM 650 in the registration and grading process. After a successful athletic fencing career which included three years as an all-American and representation of Canada internationally, he relocated to California. In 1973, while at Xerox Corp., he played an important role in the development of, and production of, the first corporate networked office. This Xerox (PARC) developed network included the first personal computers (Alto), the first high speed monochrome laser printers, the first color laser printer, and the first Ethernet-based corporate-wide electronic network. In 1977, a complete network modeled on the Xerox network was installed in President Jimmy Carter’s White House.
In 1981, Mr Silverstone provided Xerox with the packaging design for the first commercial workstation the Xerox Star 8010. In 1982 Jim Clark and Silverstone, along with some graduate students from Stanford University, founded Silicon Graphics. Mr Silverstone provided and managed the Operations Division until 1988 when he began a consulting career.
Silverstone became President and Chief Executive Officer of Netsol Technologies in 1999.
In 2000, he assumed the CEO role with Multacom, a trans-pacific telecommunications company which connected Mainland China, the United States and Taiwan.
He has served on several boards in the USA and China. While maintaining his interest in technology he is now a semi-retired advisor to newly formed companies.


Intel 80486SX

Intel's i486SX was a modified Intel 486DX microprocessor with its floating-point unit (FPU) disabled. It was intended as a lower-cost CPU for use in low-end systems. Computer manufacturers that used these processors include Packard Bell, Compaq, ZEOS and IBM.
Overview.
In the early 1990s, common applications did not need or benefit from an FPU. Among the rare exceptions were CAD applications, which could often simulate floating point operations in software, but benefited from a hardware floating point unit immensely. AMD had begun manufacturing its 386DX clone which was faster than Intel's. To respond to this new situation Intel wanted to provide a lower cost i486 CPU for system integrators, but without sacrificing the better profit margins of a "full" i486. This was accomplished through a debug feature called Disable Floating Point (DFP), by grounding a certain bond wire in the CPU package. The i486SX was introduced in mid-1991 at 20 MHz in a PGA package. Later (1992) versions of the i486SX had the FPU entirely removed for cost-cutting reasons and comes in surface-mount packages as well.
Many systems allowed the user to upgrade the i486SX to a CPU with the FPU enabled. The upgrade was shipped as the i487, which was a full-blown i486DX chip with an extra pin. The extra pin prevents the chip from being installed incorrectly. The NC# pin, one of the standard 168 pins, was used to shut off the i486SX. Although i486SX devices were not used at all when the i487 was installed, they were hard to remove because the i486SX was typically installed in non-ZIF sockets or in a plastic package that was surface mounted on the motherboard. Later OverDrive processors also plugged into the socket and offered performance enhancements as well.
External links.
Intel Datasheets


SandCraft

SandCraft, Inc., was a Silicon Valley based fabless semiconductor design company designer of microprocessors that were used as computing engines in electronics products utilizing the MIPS architecture and a series of RISC CPU chips. The markets targeted were consumer electronics, office automation, and communications applications, including Nintendo game consoles.
On , SandCraft, Inc. was acquired by Raza Microelectronics Inc, which, in turn, was acquired by NetLogic Microsystems in 2008, which itself was acquired by Broadcom in 2012.
Name.
SandCraft was named as such because sand represented silicon, the critical substrate in microprocessors, and craft to denote a design house.
History.
Norman Yeung founded SandCraft, along with Mayank Gupta as chief architect in 1996. Microprocessors with Floating point units were designed verified and contracted out to Asian manufacturing based on MIPS IV, with 64 bit instruction sets, and a later processor called SR71000, which was at the time the world's highest performance MIPS processor. They incorporated superscalar, multi-staged pipeline design, and big/little endian support modes.


ERASE.COM


GDDR SDRAM

Graphics DDR SDRAM (GDDR SDRAM) is a type of synchronous dynamic random-access memory (SDRAM) specifically designed for graphics processing units (GPUs). GDDR SDRAM is distinct from the more widely known types of DDR SDRAM, such as DDR4, although they share some of the same features—including double data rate data transfers. , GDDR SDRAM has been succeeded by GDDR2, GDDR3, GDDR4, GDDR5, GDDR5X, GDDR6, and GDDR6X.
Generations.
DDR SGRAM.
GDDR was initially known as DDR SGRAM (double data rate synchronous graphics RAM). It was commercially introduced as a 16Mb memory chip by Samsung Electronics in 1998.
GDDR2.
Main article: DDR2 SDRAM


ABA problem

In multithreaded computing, the ABA problem occurs during synchronization, when a location is read twice, has the same value for both reads, and "value is the same" is used to indicate "nothing has changed". However, another thread can execute between the two reads and change the value, do other work, then change the value back, thus fooling the first thread into thinking "nothing has changed" even though the second thread did work that violates that assumption.
The ABA problem occurs when multiple threads (or processes) accessing shared data interleave. Below is the sequence of events that will result in the ABA problem:
Although formula_1 can continue executing, it is possible that the behavior will not be correct due to the "hidden" modification in shared memory.
A common case of the ABA problem is encountered when implementing a lock-free data structure. If an item is removed from the list, deleted, and then a new item is allocated and added to the list, it is common for the allocated object to be at the same location as the deleted object due to MRU memory allocation. A pointer to the new item is thus often equal to a pointer to the old item, causing an ABA problem.
Examples.
Consider a software example (written in C++) of ABA using a lock-free stack:
/* Naive lock-free stack which suffers from ABA problem.*/
class Stack {
 std::atomic<Obj*> top_ptr;
 // Pops the top object and returns a pointer to it.
 Obj* Pop() {
 while (1) {
 Obj* ret_ptr = top_ptr;
 if (!ret_ptr) return nullptr;
 // For simplicity, suppose that we can ensure that this dereference is safe
 // (i.e., that no other thread has popped the stack in the meantime).
 Obj* next_ptr = ret_ptr->next;
 // If the top node is still ret, then assume no one has changed the stack.
 // (That statement is not always true because of the ABA problem)
 // Atomically replace top with next.
 if (top_ptr.compare_exchange_weak(ret_ptr, next_ptr)) {
 return ret_ptr;
 // The stack has changed, start over.
 // Pushes the object specified by obj_ptr to stack.
 void Push(Obj* obj_ptr) {
 while (1) {
 Obj* next_ptr = top_ptr;
 obj_ptr->next = next_ptr;
 // If the top node is still next, then assume no one has changed the stack.
 // (That statement is not always true because of the ABA problem)
 // Atomically replace top with obj.
 if (top_ptr.compare_exchange_weak(next_ptr, obj_ptr)) {
 return;
 // The stack has changed, start over.
This code can normally prevent problems from concurrent access, but suffers from ABA problems. Consider the following sequence:
Stack initially contains "top" → A → B → C
Thread 1 starts running pop:
 ret = A;
 next = B;
Thread 1 gets interrupted just before the codice_1...
 ret = A;
 next = B;
 compare_exchange_weak(A, B) // Success, top = B
 return A;
} // Now the stack is top → B → C
 ret = B;
 next = C;
 compare_exchange_weak(B, C) // Success, top = C
 return B;
} // Now the stack is top → C
delete B;
 A->next = C;
 compare_exchange_weak(C, A) // Success, top = A
Now the stack is "top" → A → C
When Thread 1 resumes:
 compare_exchange_weak(A, B)
This instruction succeeds because it finds "top" == ret (both are A), so it sets top to next (which is B). As B has been deleted the program will access freed memory when it tries to look at the first element on the stack. In C++, as shown here, accessing freed memory is undefined behavior: this may result in crashes, data corruption or even just silently appear to work correctly. ABA bugs such as this can be difficult to debug.
The real problem is not 'ABA', i.e., whether the value of A has been changed does not matter in the example. The real problem is due to B being removed from the list and the memory it occupies gets freed. Even if A has not been changed, i.e., the linked list is singly linked backwards C->B->A and tail->A, but B gets deleted and freed by another thread, the problem above still exists. This leads to another problem, i.e., if B is deleted from the list by another thread, tail would point to the deleted B. The 'ABA Problem' is therefore really 'Problem B' which has not much to do with A.
Workarounds.
Tagged state reference.
A common workaround is to add extra "tag" or "stamp" bits to the quantity being considered. For example, an algorithm using compare and swap on a pointer might use the low bits of the address to indicate how many times the pointer has been successfully modified. Because of this, the next compare-and-swap will fail, even if the addresses are the same, because the tag bits will not match. This is sometimes called ABAʹ since the second A is made slightly different from the first. Such tagged state references are also used in transactional memory. Although a tagged pointer can be used for implementation, a separate tag field is preferred if double-width CAS is available.
If "tag" field wraps around, guarantees against ABA do not stand anymore. However, it has been observed that on currently existing CPUs, and using 60-bit tags, no wraparound is possible as long as the program lifetime (that is, without restarting the program) is limited to 10 years; in addition, it was argued that for practical purposes it is usually sufficient to have 40-48 bits of tag to guarantee against wrapping around. As modern CPUs (in particular, all modern x64 CPUs) tend to support 128-bit CAS operations, this can allow firm guarantees against ABA.
Intermediate nodes.
A correct but expensive approach is to use intermediate nodes that are not data elements and thus assure invariants as elements are inserted and removed [Valois].
Deferred reclamation.
Another approach is to defer reclamation of removed data elements. One way to defer reclamation is to run the algorithm in an environment featuring an automatic garbage collector; a problem here however is that if the GC is not lock-free, then the overall system is not lock-free, even though the data structure itself is.
Another way to defer reclamation is to use one or more hazard pointers, which are pointers to locations that otherwise cannot appear in the list. Each hazard pointer represents an intermediate state of an in-progress change; the presence of the pointer assures further synchronization [Doug Lea]. Hazard pointers are lock-free, but can only track at most a fixed number of elements per thread as being in-use.
Yet another way to defer reclamation is to use read-copy update (RCU), which involves enclosing the update in an RCU read-side critical section and then waiting for an RCU grace period before freeing any removed data elements. Using RCU in this way guarantees that any data element removed cannot reappear until all currently executing operations have completed. RCU is lock-free, but isn't suitable for all workloads.
Some architectures provide "larger" atomic operations such that, as example, both forward and backward links in a doubly linked list can be updated atomically; while this feature is architecture-dependent, it, in particular, is available for x86/x64 architectures (x86 allows for 64-bit CAS, and all modern x64 CPUs allow for 128-bit CAS) and IBM's z/Architecture (which allows for up to 128-bit CAS).
Some architectures provide a load linked, store conditional instruction in which the store is performed only when there are no other stores of the indicated location. This effectively separates the notion of "storage contains value" from "storage has been changed". Examples include DEC Alpha, MIPS, PowerPC, RISC-V and ARM (v6 and later).


Pentium FDIV bug

The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R. Nicely, a professor of mathematics at Lynchburg College. Missing values in a lookup table used by the FPU's floating-point division algorithm led to calculations acquiring small errors. While these errors would in most use-cases only occur rarely and result in small deviations from the correct output values, in certain circumstances the errors can occur frequently and lead to more significant deviations.
The severity of the FDIV bug is debated. Though rarely encountered by most users ("Byte" magazine estimated that 1 in 9 billion floating point divides with random parameters would produce inaccurate results), both the flaw and Intel's initial handling of the matter were heavily criticized by the tech community.
In December 1994, Intel recalled the defective processors in what was the first full recall of a computer chip. In January 1995, Intel announced "a pre-tax charge of $475 million against earnings, ostensibly the total cost associated with replacement of the flawed processors."
Description.
In order to improve the speed of floating-point division calculations on the Pentium chip over the 486DX, Intel opted to replace the shift-and-subtract division algorithm with the Sweeney, Robertson, and Tocher (SRT) algorithm. The SRT algorithm can generate two bits of the division result per clock cycle, whereas the 486's algorithm could only generate one. It is implemented using a programmable logic array with 2,048 cells, of which 1,066 cells should have been populated with one of five values: . When the original array for the Pentium was compiled, five values were not correctly downloaded into the equipment that etches the arrays into the chips – thus five of the array cells contained zero when they should have contained +2.
As a result, calculations that rely on these five cells acquire errors; these errors can accumulate repeatedly owing to the recursive nature of the SRT algorithm. In pathological cases the error can reach the fourth significant digit of the result, although this is rare. The error is usually confined to the ninth or tenth significant digit.
Only certain combinations of numerator and denominator trigger the bug. One commonly-reported example is dividing 4,195,835 by 3,145,727. Performing this calculation in any software that used the floating-point coprocessor, such as Windows Calculator, would allow users to discover whether their Pentium chip was affected.
The correct value of the calculation is:
When converted to the hexadecimal value used by the processor, 4,195,835 = 0x4005FB and 3,145,727 = 0x2FFFFF. The '5' in 0x4005FB triggers the access to the 'empty' array cells. As a result, the value returned by a flawed Pentium processor is incorrect at or beyond four digits:
Discovery and response.
Thomas Nicely, a professor of mathematics at Lynchburg College, had written code to enumerate primes, twin primes, prime triplets, and prime quadruplets. Nicely noticed some inconsistencies in the calculations on June 13, 1994, shortly after adding a Pentium system to his group of computers, but was unable to eliminate other factors (such as programming errors, motherboard chipsets, etc.) until October 19, 1994. On October 24, 1994, he reported the issue to Intel. Intel had reportedly become aware of the issue independently by June 1994, and had begun fixing it at this point, but chose not to publicly disclose any details or recall affected CPUs.
On October 30, 1994, Nicely sent an email describing the bug to various academic contacts, requesting reports of testing for the flaw on 486-DX4s, Pentiums and Pentium clones. The bug was quickly verified by others, and news of it spread quickly on the Internet. The bug acquired the name "Pentium FDIV bug" from the x86 assembly language mnemonic for floating-point division, the most frequently used instruction affected.
The story first appeared in the press on November 7, 1994, in an article in "Electronic Engineering Times", "Intel fixes a Pentium FPU glitch" by Alexander Wolfe, and was subsequently picked up by CNN in a segment aired on November 22. It was also reported on by the "New York Times" and the "Boston Globe", making the front page in the latter.
At this point, Intel acknowledged the floating-point flaw, but claimed that it was not serious and would not affect most users. Intel offered to replace processors to users who could prove that they were affected. However, although most independent estimates found that the bug would have a very limited impact on most users, it caused significant negative press for the company. IBM paused the sale of PCs containing Intel CPUs, and Intel's stock price decreased significantly. The motive behind IBM's decision was questioned by some in the industry; IBM produced the PowerPC CPUs at the time, and potentially stood to benefit from any reputational damage to the Pentium or Intel as a company. However, the decision led to corporate buyers of PC equipment demanding replacements of existing Pentium CPUs, and soon afterwards other PC manufacturers began offering "no questions asked" replacements of flawed Pentium chips.
The growing dissatisfaction with Intel's response led to the company offering to replace all flawed Pentium processors on request on December 20. On January 17, 1995, Intel announced "a pre-tax charge of $475 million against earnings, ostensibly the total cost associated with replacement of the flawed processors." This is equivalent to $ in . Intel was criticised for barring resellers and OEMs from participating in the recall programme, requiring end-users to replace chips themselves. Intel's justification for this, posted on its support web page, was that "it is the individual decision of the end user to determine if the flaw is affecting their application accuracy".
A 1995 article in "Science" describes the value of number theory problems in discovering computer bugs and gives the mathematical background and history of Brun's constant, the problem Nicely was working on when he discovered the bug.
Intel's response to the FDIV bug has been cited as a case of the public relations impact of a problem eclipsing the practical impact of said problem on customers. While most users were unlikely to encounter the flaw in their day-to-day computing, the company's initial reaction to not replace chips unless customers could guarantee they were affected caused pushback from a vocal minority of industry experts. The subsequent publicity generated shook consumer confidence in the CPUs, and led to a demand for action even from people unlikely to be affected by the issue. Andrew Grove, Intel's CEO at the time was quoted in the "Wall Street Journal" as saying "I think the kernel of the issue we missed [...] was that we presumed to tell somebody what they should or shouldn't worry about, or should or shouldn't do".
In the aftermath of the bug and subsequent recall, there was a marked increase in the use of formal verification of hardware floating point operations across the semiconductor industry. Prompted by the discovery of the bug, a technique applicable to the SRT algorithm called "word-level model checking" was developed in 1996. Intel went on to use formal verification extensively in the development of later CPU architectures. In the development of the Pentium 4, symbolic trajectory evaluation and theorem proving were used to find a number of bugs that could have led to a similar recall incident had they gone undetected. The first Intel microarchitecture to use formal verification as the primary method of validation was Nehalem, developed in 2008.
Affected models.
The FDIV bug affects the 60 and 66 MHz Pentium P5 800 in stepping levels prior to D1, and the 75, 90, and 100 MHz Pentium P54C 600 in steppings prior to B5. The 120 MHz P54C and P54CQS CPUs are unaffected.
Software patches.
Various software patches were produced by manufacturers to work around the bug. One specific algorithm, outlined in a paper in "IEEE Computational Science & Engineering", is to check for numerators and denominators that will trigger the access to the programmable logic array cells that erroneously contain zero, and if found, multiply both numbers by 15/16. This takes them out of the 'buggy' range. However, doing this has a significant speed penalty – in some cases doubling the time taken to perform the calculation.
The main challenge faced by software companies was implementing the fix in pre-existing software, much of which relied on libraries outside their control. Some companies, such as Wolfram Research, opted to directly patch the machine code of existing executables to replace the FDIV opcode with an illegal instruction. This would then trigger an exception that an exception handler (also patched in) would catch. From here, arbitrary code could be executed to work around the bug.
Microsoft offered operating system level workarounds in versions of Windows up to Windows XP. Utilities were included with the operating system to check for the presence of the bug and disable the FPU if found.


DigitaOS

DigitaOS was a short lived digital camera operating system created by Flashpoint Technology and used on various Kodak, Pentax, and HP cameras in the late 1990s. DigitaOS debuted with the Kodak DC220 on , and was released on a total of 11 camera models before it was abandoned in 2001. DigitaOS was notable for its ability to run third party software, a concept that was not again realized until the release of various Android based digital cameras in the early 2010s.
DigitaOS applications were programmed either as JIT compiled scripts using "Digita Script", or AOT compiled programs written in C using an official SDK. The operating system abstracted away most camera functionality and hardware platform differences, allowing software to be compatible with most DigitaOS cameras. Additionally, DigitaOS handled the GUI presented to the user and basic camera functionality.
Because of its ability to run third party software, several games were ported to it. The most notable of these being DOOM and MAME.