The IBM RT (or PC/RT or 6150 in Europe) was a 32-bit RISC machine. In fact 'RT' meant 'RISC Technology' where RISC itself was initials of Reduced Instruction Set Computers. This machine was IBM's first try into the single-user workstation world and was the ancestor of the RS/6000 range.
The advantages of RISC technology were smaller processor chips, since they needed less on-chip storage for the instruction set, faster signal transfer between devices, and faster instruction execution since the reduced set was designed so that most instructions was executed in a single clock cycle.
The RISC processor of the 6150 was called ROMP for Reshearch Office Products Division. Its study started in IBM Texas labs in 1977 and a prototype form ran in 1978
There were two RT models, the floor-standing 6150 and the desktop 6151. The differences between them lie in the positioning of some I/O ports and in the storage options available.
Despite processor incompatibility with MS-DOS software, the 6150 could run PC software thanks to a PC expansion card holding a Intel 80286 and designed to fit in one of the AT compatible slots of the 6150. the motherboard featured four 32-bit expansion slots to hold the ROMP board, an optional floating-point accelerator board, and two 2 MB RAM boards; two 8-bit and six 16-bit PC slots.
The 6150 operating system was called AIX for Advanced Interactive eXecutive. It succeded to IBM OSes. In fact, it was just an Unix System V with Berkeley 4.2 enhancements and IBM adds for the 6150 environment. Among these adds, the VRM (Virtual Ressource Manager) handled the interface between the Unix kernel and the specific 6150 harware it ran on. A DOS shell was also provided for MS-DOS applications.
Nowadays, one finds RISC processors mainly in numerous small devices like PalmTops or mobile phones. Apple and IBM also use them today, the biggest examples being the PowerPC 7455 (G4) and PowerPC G5 Processor, mostly used in the Power Macintosh and Powerbook series of computers. Many Proprietary Unix systems used them up until only a few years ago (Sun, Silicon Graphics).
BUILT IN LANGUAGE
Special RT 102-key keyboard, PC-AT layout.
ROMP RISC processor
5.88, 10 or 12.5 MHz (170, 100 or 80ns cycle time)
Memory Management Unit (MMU), optional 20 MHz Motorola 68881 Math coprocessor
From 1 MB to 16 MB
80 chars. x 25 lines
720 x 512 (mono or colour), 1024 x 768 (mono)
SIZE / WEIGHT
2 x serial ports
BUILT IN MEDIA
1 or 2 5.25'' 1.2 MB floppy disc drives Up to three 40 MB or 70 MB hard disks