“They also decided on an open architecture, so that other manufacturers could produce and sell peripheral components and compatible software without purchasing licenses. IBM also sold an IBM PC Technical Reference Manual which included complete circuit schematics, a listing of the ROM BIOS source code, and other engineering and programming information.”

Djohnston: I should have clarified – no one at IBM. Networks had been around for decades at IBM but they felt this was a “toy” and the sales projections were woefully low. It has been well documented that IBM didn’t take it seriously until it threatened the big iron.

You said, “No one in 1980 could predict the importance of connecting PCs together.” Hmmm… John Brunner wrote The Shockwave Rider, first published in 1975. It is notable for its hero’s use of computer cracking skills, and for the coining of the word “worm” to describe a program that propagates itself through a computer network.

A little more research, maybe?

If it fails to give me that then I won’t buy it.

IBM published the source to their BIOS in the manuals that anyone could buy. We still have the XT and AT sets.

Compaq and Phoenix Technology were responsible for opening up the market to beige-box cloning. PTI did a Chinese-wall clean-room reimplementation of the IBM BIOS for Compaq (one team generated specifications based on the IBM code they saw, then tossed the specs over the wall to the coding team to follow, so nobody who coded ever saw the original IBM code), thus allowing Compaq to vend its own machines without licensing the BIOS from IBM, and that started the beige-box gold rush. IBM’s attempt to then recapture the market with the more-heavily-restricted PS/2 Microchannel family failed, as customers and vendors largely ignored it in favor of enhancements to the PC-AT architecture aka Industry Standard Architecture, ISA, and that’s when IBM lost control of that market for good.

IBM’s BIOS, as of the last time I looked, was vended under the SurePath tradename.