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Personal System/2 (PS/2) was IBM’s third generation of PCs introduced in 1987. The PS/2 was an advanced proprietary computer architecture launched by IBM in an attempt to regain control of the PC market.
Higher price tags and the public’s preference for the existing computer architecture lead to the failure of PS/2. However, many innovations derived from PS/2 architecture were successful for many years; these included the 16550 UART, 1440 KB 3.5-inch floppy disk format, 72-pin SIMMs, the PS/2 keyboard and mouse ports, and the VGA video standard.
The PS/2 architecture was quite different. It was designed to be compatible with the PC/XT/AT line of computers popular in the PC clone market. PS/2 architecture had 2 BIOSs (ABIOS and CBIOS) for additional security and compatibility and Micro Channel Architecture for superior bus communications speed. It included special connection ports for mouse and keyboards (still in use into the 21st-century, and called PS/2 interfaces) and incorporated a new frame buffer known as VGA (Video Graphics Array) which replaced the previous EGA (Enhanced Graphics Adapter) standard. PS/2 used the 15-pin mini-D connector for video out and used RGB signals allowing increases in color depth (i.e. increased levels of gray}. The PS/2 line was the first to use 3.5” floppy disks (common by 1987) as standard and introduced the 72-pin RAM SIMM which became the de facto standard for RAM by the mid-1990s.
The PS/2 family of computers came in many successive models. Models 25 and 30 were ISA-based, came with 720 MB 3.5” floppy disk drives, an ST506-compatible hard drive controller and MCGA graphics. Models 35 and 40 had Intel 386SX or IBM 386SLC processors. Models 50 and 60 and all later models used a Micro Channel bus and mostly ESDI or SCSI hard drives; the 50 and 60 models used the Intel 286 processor. Models 70 and 80 used the Intel 386DX processor, while the Models 90 and 95 included options from the 20 MHz Intel 486 to the 90 MHz Pentium processors and were interchangeable. Each model came with an associated 4 digit IBM numbers; e.g. the Model 90 was IBM 8590 or IBM 8595.
Although many PS/2 models had lifetimes well into the late 1990s, the computer line was largely unsuccessfully marketed, and suffered massive financial losses in that decade. The IBM PS/2 eventually lost its reputation as the single largest PC manufacturer to Compaq and then later to Dell.