The IBM PS/2: 25 years of PC history

Here's a fond look back at the Personal System/2 series of PCs, which embarrassed IBM in the 1980s but shaped the modern PC you know today.

By Benj Edwards, PC World |  Hardware, BIOS, compaq

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.

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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.

Attack of the Clones

When IBM created the PC in 1981, it used a large number of easily obtainable, off-the-shelf components to construct the machine. Just about any company could have put them together into a computer system, but IBM added a couple of features that would give the machine a flavor unique to IBM. The first was its BIOS, the basic underlying code that governed use of the machine. The second was its disk operating system, which had been supplied by Microsoft.

When Microsoft signed the deal to supply PC-DOS to IBM, it included a clause that allowed Microsoft to sell that same OS to other computer vendors--which Microsoft did (labeling it "MS-DOS") almost as soon as the PC launched.

That wasn't a serious problem at first, because those non-IBM machines, although they ran MS-DOS, could not legally utilize the full suite of available IBM PC software and hardware add-ons.

As the IBM PC grew in sales and influence, other computer manufacturers started to look into making PC-compatible machines. Before doing so, they had to reverse-engineer IBM's proprietary BIOS code using a clean-room technique to spare themselves from infringing upon IBM's copyright and trademarks.

First PC Clone: MPC 1600

Originally published on PC World |  Click here to read the original story.
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