IBM RT PC

The IBM RT PC (RISC Technology Personal Computer) is a family of workstation computers from IBM introduced in 1986. These were the first commercial computers from IBM that were based on a reduced instruction set computer (RISC) architecture. The RT PC uses IBM's proprietary ROMP microprocessor, which commercialized technologies pioneered by IBM Research's 801 experimental minicomputer (the 801 was the first RISC). The RT PC runs three operating systems: AIX, the Academic Operating System (AOS), and Pick.

The RT PC's specifications were regarded as "less than impressive" compared to contemporary workstations by its competitors in that particular market, although the product was deemed deserving of "a healthy amount of respect", particularly with the prospect of IBM as "a serious competitor" who, despite having a product whose performance was an estimated 18 months behind other vendors, would potentially be able to catch up quickly by applying the company's renowned technological capabilities. Given such performance limitations, the RT PC had little commercial success as a result. IBM responded by introducing the RS/6000 workstations in 1990, which used a new IBM-proprietary RISC processor, the POWER1. All RT PC models were discontinued by May 1991.

Two basic types were produced: a floor-standing desk-side tower (IBM 6150), and a desktop (IBM 6151). Both types featured a special board slot for the processor card, as well as machine-specific RAM cards. Each machine had one processor slot, one co-processor slot, and two RAM slots.

There were three versions of the processor card:

All RT PCs supported up to 16 MB of memory. Early models were limited to 4 MB of memory because of the capacity of the DRAM ICs used, later models could have up to 16 MB. I/O was provided by eight ISA bus slots. Storage was provided by a 40 or 70 MB hard drive, upgradeable to 300 MB. 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 4 Mbit/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.

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 8 MB 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.

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.