IBM Personal System/2 - Technology - Models

Models

At launch, the PS/2 family comprised the Model 30, 50, 60 and 80; the Model 25 was launched a few months later.

The PS/2 Models 25 and 30 (IBM 8525 and 8530 respectively) were ISA-based (in other words, essentially IBM PC-like systems in a different form factor) systems, originally only available with Intel 8086 CPUs. These machines also differed from other PS/2 models in having 720k floppy disk drives, an ST506-compatible hard drive controller and MCGA graphics. The hard drives were available as an optional part; however, many of these entry-level machines were sold without hard drives due to the high cost.

The Model 25 featured an integrated monochrome or color monitor to compete with the Apple Macintosh as an integrated system for educational environments. An external "paper white" monochrome screen was also available as a cost-saving model instead of the standard VGA display; this was often paired with the Model 30.

Later ISA PS/2 models comprised the Model 30-286 (a Model 30 with an Intel 286 CPU), Model 35 (IBM 8535) and Model 40 (IBM 8540) with Intel 386SX or IBM 386SLC processors.

The higher-numbered models were equipped with the MCA bus and mostly ESDI or SCSI hard drives (models 60-041 and 80-041 being MFM based). PS/2 Models 50 (IBM 8550) and 60 (IBM 8560) used the Intel 286 processor, the PS/2 Models 70 (IBM 8570) and 80 used the 386DX, while the medium-performance PS/2 Model 55SX (IBM 8555-081) used the 16/32-bit 386SX processor. Later Model 70 and 80 variants (B-xx) also used 25 MHz Intel 486 processors, in a complex called the Power Platform.

The PS/2 Models 90 (IBM 8590/9590) and 95 (IBM 8595/9595/9595A) used Processor Complex daughterboards holding the CPU, memory controller, MCA interface, and other system components. The available Processor Complex options ranged from the 20 MHz Intel 486 to the 90 MHz Pentium and were fully interchangeable. The IBM PC Server 500, which has a motherboard identical to the 9595A, also uses Processor Complexes.

Other later MicroChannel PS/2 models included the Model 65SX with a 16 MHz 386SX; various Model 53 (IBM 9553), 56 (IBM 8556) and 57 (IBM 8557) variants with 386SX, 386SLC or 486SLC2 processors; the Models 76 and 77 (IBM 9576/9577) with 486SX or 486DX2 processors respectively; and the 486-based Model 85 (IBM 9585).

The IBM PS/2E (IBM 9533) was the first Energy Star compliant personal computer. It had a 50 MHz IBM 486SLC processor, an ISA bus, four PC card slots, and an IDE hard drive interface. The environmentally friendly PC borrowed many components from the ThinkPad line and was composed of recycled plastics, designed to be easily recycled at the end of its life, and used very little power.

IBM also produced several portable and laptop PS/2s, including the Model L40 (ISA-bus 386SX), N33 (IBM's first notebook-format computer from year 1991, Model 8533, 386SX), N51 (386SX/SLC), P70 (386DX) and P75 (486DX2).

The IBM PS/2 Server 195 and 295 (IBM 8600) were 486-based dual-bus MCA network servers supporting asymmetric multiprocessing, designed by Parallan Computer Inc.

The IBM PC Server 720 (IBM 8642) was the largest MCA-based server made by IBM, although it was not, strictly speaking, a PS/2 model. It could be fitted with up to six Intel Pentium processors interconnected by the Corollary C-bus and up to eighteen SCSI hard disks. This model was equipped with seven combination MCA/PCI slots.

The IBM ThinkPad 700C, aside from being labeled "700C PS/2" on the case, featured MCA and a 486SLC CPU.

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