slots. The 1616 shared this backplane with a platform developed by Andrew Morton for Keno Computer Systems, allowing the 1616 to use expansion boards developed for the Keno Computer Systems platform (primarily the 34010 graphics coprocessor), although the form-factor was different, which left the KCS cards sticking out of the top of the 1616 case! Disk controller card The disk controller card contains: A Zilog Z80 processor running at 8 MHz 32 kibibytes of ROM 64 kibibytes of Static RAM a WD1772 floppy disk controller dual RS-232 serial ports using a Zilog Z8530 An NCR5380 SCSI controller The coprocessor is able to run ZRDOS (a CP/M clone), or can act as a smart disk controller. Memory expansion card The memory card: accepts between 1 and 4 megabytes of Dynamic RAM in 1 megabyte increments, has an optional memory management unit implemented in fast Static RAM and PALs, Another NCR5380 SCSI hard disk interface. This SCSI controller was mapped into the 68000's address space, and was considerably faster than the one on the Z80 coprocessor card. 34010 graphics coprocessor card The TMS34010 card was developed by Andrew Morton for Keno Computer Systems. The 34010 was a bit-addressable graphics processor with instructions for two-dimensional graphics primitives and arbitrary width arithmetic operations on pixel data. User developed cards Graham Redwood developed an Ethernet card (wire-wrap or Speedwire prototype?). Philip Hutchison developed a Motorola 68030 coprocessor card (small run of working double sided PCBs). Kevin Bertram developed a Transputer card, an Eprom Programmer, and an IO card. (The Eprom Programmer was manufactured under licence by Timothy Ward of Silicon Supply and Manufacturing.) (The IO card design was used in development by Silicon Supply and Manufacturing of a CNC PC Drill which had a provisional patent, but never released as a kit.) Other one-off interface cards were developed for specific projects, including a numerically controlled sheet metal spinning machine controller, several EEPROM programmers, etc. Operating systems 1616/OS 1616/OS was initially little more than a powerful monitor, with commands for dumping and modifying memory, loading and saving to tape, and a built in macro assembler and full screen editor. Over time, the operating system gained a hierarchical file system, preemptive multitasking, support for multiple users with access controls (although no memory protection), lightweight threads, message passing primitives and pipes. Ultimately, the operating system had around 250 system calls, and 78 commands built into the shell. The