At launch, the PS/2 family comprised the Model 30, 50, 60 and 80; the Model 25 was launched a few months later.
These models were in the strange position of being incompatible with the IBM-compatible hardware standards previously established by IBM and adopted in the PC industry.
The PS/2 Models 25 and 30 (IBM 8525 and 8530, respectively) were the lowest-end models in the lineup and meant to replace the IBM PC and XT. Model 25s came with either an 8086 CPU running at 8 MHz, 512 KB of RAM, and 720 KB floppy disks, or 80286 CPU. The 8086s had ISA expansion slots and a built-in MCGA monitor, which could be either color or monochrome, while the 80286 models came with VGA monitor and ISA expansion slots.
30-pin SIMM memory was typical for the launch models but eventually IBM switched to the 72-pin SIMM. IBM used some proprietary steps to prevent mass market RAM from working without some modifications.
Hard disks typically were MFM or ESDI. Some models came with a SCSI hard disk. Typically, desktop PS/2 models only permitted use of one hard drive inside the computer case. Additional storage could be attached externally using the optional SCSI interface.
The PS/2 brought the IBM Microchannel slot that was strictly licensed so the industry immediately balked at adopting it. The PS/2 also brought new small DIN connectors for the keyboard and mouse.
Most bought the affordable 8513 640×480 12″ monitor for basic work. The larger 8512 640×480 14″ monitor is more expensive. The higher resolution 8514 was interlaced and flickered badly. The D-sub 15-pin video connector was standard for all of IBM’s new monitors.
IBM’s PS/2 was designed to remain software compatible with their PC/AT/XT line of computers upon which the large PC clone market was built, but the hardware was quite different. On BIOS is compatible with the 8088 mode which is what PC-DOS uses. The other BIOS runs in protected mode allowing the new 80386 to be able to run other operating systems.
In time, IBM sold over 3 million machines. The PS/2 was a success for IBM at a time of a growing competitive industry.