on-board memory, while an enhanced advanced floating point accelerator was standard. The models 130, 135, and B35 used these cards. They were announced on July 19, 1988. All RT PCs supported up to 16MB of memory. Early models were limited to 4MB of memory because of the capacity of the DRAM ICs used, later models could have up to 16MB. I/O was provided by eight ISA bus slots. Storage was provided by a 40 or 70MB hard drive, upgradeable to 300MB. External SCSI cabinets could be used to provide more storage. Also standard were a mouse and either a 720×512 or 1024×768 pixel-addressable display, and a 4Mbit/s Token Ring network adapter or 10BASE2 Ethernet adapter. For running CADAM, a computer-aided design (CAD) program, an IBM 5080 or 5085 graphics processor could be attached. The 5080 and 5085 were contained in a large cabinet that would have been positioned alongside the RT PC. The 5080 was used with a 1,024- by 1,024-pixel IBM 5081 display. 6152 Academic System The 6152 Academic System was a PS/2 Model 60 with a RISC Adapter Card, a Micro Channel board containing a ROMP, its support ICs, and up to 8MB of memory. It allowed the PS/2 to run ROMP software compiled for the AOS. AOS was downloaded from a RT PC running AOS, via a LAN TCP/IP interface. Software One of the novel aspects of the RT design was the use of a microkernel. The keyboard, mouse, display, disk drives and network were all controlled by a microkernel, called Virtual Resource Manager (VRM), which allowed multiple operating systems to be booted and run at the same time. One could "hotkey" from one operating system to the next using the Alt-Tab key combination. Each OS in turn would get possession of the keyboard, mouse and display. Both AIX version 2 and the Pick operating system were ported to this microkernel. Pick was unique in being a unified operating system and database, and ran various accounting applications. It was popular with retail merchants, and accounted for about 4,000 units of sales. The primary operating system for the RT was AIX version 2. Much of the AIX v2 kernel was written in a variant of the PL/I programming language, which proved troublesome during the migration to AIX v3. AIX v2 included full TCP/IP networking support, as well as SNA, and two networking file systems: NFS, licensed from Sun