Micro Channel vs. EISA and PCI

Start-ups ganged up against IBM in PC market.

IBM faced off against the Gang of Nine in the battle of the PC buses during the 1980s and 1990s and Big Blue eventually gave in.

It was the best of times, it was the worst of times for IBM, the developer of the proprietary, yet oh-so-capable Micro Channel (MCA) bus. Created in 1987 for use in its PS/2 personal computers, the 16- or 32-bit bus was designed to overcome the limitations of the ISA bus, which suffered from a slow speed, limited interrupts and a lack of bus-mastering support. IBM had the misfortune of butting heads with a bus developed in 1989 by IBM competitors – the EISA bus, which was backward-compatible with older PC- and XT-bus computers and also offered bus-mastering support. 

The IBM competitors, the so-called Gang of Nine -- AST Research, Compaq Computer, Epson, HP, NEC, Olivetti, Tandy, WYSE and Zenith Data Systems – reacted to IBM’s proprietary architecture and refused to license it for use in their servers. The gang prevailed and their EISA design, which was used in clone PCs, soon won out

Walt Thirion, formerly CTO for Level One Communications of Sacramento, remembers the Micro Channel/EISA bus wars and does not want them repeated. As president and CEO of Thomas-Conrad, Thirion had to manufacture network interface adapters for both EISA and Micro Channel computers. You might ask him if that was a burden making adapters to two different bus specifications and Thirion, like the CEOs of Standard Microsystems and 3Com, would have said 'Hell, yes, it was a pain for little return.”

The Gang of Nine wasn’t the only group that riled IBM. The Music Corporation of America, then a powerhouse in the music publishing field, filed a suit claiming its rights to the MCA acronym. IBM uncharacteristically withdrew its use of the acronym – going forward the Micro Channel bus would be known as just that.

In 1996, IBM caved in to the EISA bus backers when it introduced computers that used the technology. In spite of the spat between IBM and the rest of the PC industry, desktop PCs continued to use the EISA bus, until the introduction of PCI. Today, neither server nor desktop PCs use MCA (whoops Micro Channel) or EISA – they all use PCI and its successor PCI-Express.

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