Twenty-five years ago, IBM announced the Personal System/2 (PS/2), a new line of IBM PC-compatible machines that capped an era of profound influence on the personal computer market.

By the time of the PS/2's launch in 1987, IBM PC clones--unauthorized work-alike machines that could utilize IBM PC hardware and software--had eaten away a sizable portion of IBM's own PC platform. Compare the numbers: In 1983, IBM controlled roughly 76 percent of the PC-compatible market, but in 1986 its share slipped to 26 percent.

IBM devised a plan to regain control of the PC-compatible market by introducing a new series of machines--the PS/2 line--with a proprietary expansion bus, operating system, and BIOS that would require clone makers to pay a hefty license if they wanted to play IBM's game. Unfortunately for IBM, PC clone manufacturers had already been playing their own game.

In the end, IBM failed to reclaim a market that was quickly slipping out of its grasp. But the PS/2 series left a lasting impression of technical influence on the PC industry that continues to this day.

Read the rest: http://www.pcworld.com/article/258989/the_ibm_ps2_25_years_of_pc_history.html

This was first PC compatible computer I worked on.
You can still find remains of this computers. PS/2 ports are still alive and present on any good MB. And, of course, amazing keyboards. Get one if you don't have it, and during celebration of 50 years you'll be still typing on it.