What with the arrival of the category-defining Commodore VIC-20 and the dramatic growth of the British PC market, 1981 has provided us with no shortage of new machines and other technical developments to talk about. Yet I’ve saved the biggest event of all for last: the introduction of the IBM PC, the debut of an architecture that is still with us over 30 years later. As such a pivotal event in the history of computing, there’s been plenty written about it already, and no small amount of folklore of dubious veracity has also clustered around it. Still, it’s not something we can ignore here, for the introduction of the IBM PC in late 1981 marks the end of the first era of PCs as consumer products as surely as the arrival of the trinity of 1977 spelled the end of the Altair era of home-built systems. So, I’ll tell the tale here again. Along the way, I’ll try to knock down some pervasive myths.

One could claim that the IBM PC was not really IBM’s first PC at all. In September of 1975 the company introduced the IBM 5100, their first “portable” computer. (“Portable” meant that it weighed just 55 pounds and you could buy a special travel case to lug it around in.)

The 5100 was not technically a microcomputer; it used a processor IBM had developed in-house called the PALM which was spread over an entire circuit board rather than being housed in a single microchip. From the end user’s standpoint, however, that made little difference; certainly it would seem to qualify as a personal computer if not a microcomputer. It was a self-contained, Turing complete, programmable machine no larger than a suitcase, with a tape drive for loading and saving programs, a keyboard, and a 5-inch screen all built right in along with 16 K or more of RAM. What made the 5100 feel different from the first wave of PCs were its price and its promoted purpose. The former started at around $10,000 and could quickly climb to the $20,000 range. As for the latter: IBM pushed the machine as a serious tool for field engineers and the like in remote locations where they couldn’t access IBM’s big machines, not as anything for fun, education, hacking, or even office work. The last of these at least changed with two later iterations of the concept, the 5110 and 5120, which were advertised as systems suitable for the office, with accounting, database, and even word processing applications available. Still, the prices remained very high, and actually outfitting one for this sort of office work would entail connecting it to a free-standing disk array that was larger than the machine itself, making the system look and feel more like a minicomputer and less like a PC. It’s nevertheless telling that, although it was almost never referred to by this name, the IBM PC when it finally arrived had the official designation of (with apologies to Van Halen) the IBM 5150, a continuation of the 5100 line of portable computers rather than an entirely new thing — this even though it shared none of the architecture of its older siblings.

In February of 1978 IBM began working on its first microcomputer — and it still wasn’t the IBM PC. It was a machine called the System/23 Datamaster.

Designed once again for an office environment, the Datamaster was built around an Intel 8085 microprocessor. It was large and heavy (95 pounds), and still cost in the $10,000 range, which combined with its very business-oriented, buttoned-down personality continued to make it feel qualitatively different from machines like the Apple II. Yet it was technically a microcomputer. IBM was a huge company with a legendarily labyrinthine bureaucracy, meaning that projects could sometimes take an inordinately long time to complete. Despite the Datamaster project predating the PC project by two years, the former didn’t actually come out until July of 1981, just in time to have its thunder stolen by the announcement of the IBM PC the following month. Still, if the question of IBM’s first microcomputer ever comes up in a trivia game, there’s your answer.

The machine that would become known as the real IBM PC begins, of all places, at Atari. Apparently feeling their oats in the wake of the Atari VCS’s sudden Space Invaders-driven explosion in popularity and the release of their own first PCs, the Atari 400 and 800, they made a proposal to IBM’s chairman Frank Cary in July of 1980: if IBM wished to have a PC of their own, Atari would deign to build it for them. Far from being the hidebound mainframer that he’s often portrayed as, Cary was actually something of a champion of small systems — even if “small systems” in the context of IBM often meant something quite different from what it meant to the outside world. Cary turned the proposal over to IBM’s Director of Entry Systems, Bill Lowe, based out of Boca Raton, Florida. Lowe in turn took it to IBM’s management committee, who pronounced it “the dumbest thing we’ve ever heard of.” (Indeed, IBM and Atari make about the oddest couple imaginable.) But at the same time, everyone knew that Lowe was acting at the personal behest of the chairman, not something to be dismissed lightly if they cared at all about their careers. So they told Lowe to assemble a team to put together a detailed proposal for how IBM could build a PC themselves — and to please come back with it in just one month.

Lowe assembled a team of twelve or thirteen (sources vary) to draft the proposal. In defiance of all IBM tradition, he deliberately kept the team small, the management structure informal, hoping to capture some of the hacker magic that had spawned PCs in the first place. His day-to-day project manager, Don Estridge, said, “If you’re competing against people who started in a garage, you have to start in a garage.” One might have expected IBM, the Goliath of the computer industry, to bludgeon their way into the PC market. Indeed, and even as they congratulated themselves for having built this new market using daring, creativity, and flexibility stolid IBM could not hope to match, many PC players lived in a sort of unvoiced dread of exactly this development. IBM, however, effectively decided to be a good citizen, to look at what was already out there and talk to those who had built the PC market to find out what was needed, where a theoretical IBM PC might fit. In that spirit, Jack Sams, head of software development, recommended that they talk to Microsoft. Sams was unusually aware of the PC world for an IBMer; he had actually strongly pressed for IBM to buy the BASIC for the Datamaster from Microsoft, but had been overruled in favor of an in-house effort. “It just took longer and cost us more,” he later said. Sams called Bill Gates on July 21, 1980, asking if he (Sams) could drop by their Seattle office the next day for a friendly chat about PCs. “Don’t get too excited, and don’t think anything big is about to happen,” he said.

Gates and Steve Ballmer, his right-hand man and the only one in this company of hackers with a business education, nevertheless both realized that this could be very big indeed. When Sams arrived with two corporate types in tow to function largely as “witnesses,” Gates came out personally to meet them. (Sams initially assumed that Gates, who still had the face, physique, and voice of a twelve-year-old, was the office boy.) Sams immediately whipped out the non-disclosure agreement that was standard operating procedure for IBM. Gates: “IBM didn’t make it easy. You had to sign all these funny agreements that sort of said IBM could do whatever they wanted, whenever they wanted, and use your secrets however they felt. So it took a little bit of faith.” Nevertheless, he signed it immediately. Sams wanted to get a general sense of the PC market from Gates, a man who was as intimately familiar with it as anyone. In this respect, Gates was merely one of a number of prominent figures he spoke with. However, he also had an ulterior motive: to see just what kind of shop Gates was running, to try to get a sense of whether Microsoft might be a resource his team could use. He was very impressed.

After consulting with Gates and others, Lowe presented a proposal for the machine that IBM should build on August 8. Many popular histories, such as the old PBS Triumph of the Nerds, give the impression that the IBM PC was just sort of slapped together in a mad rush. Actually, a lot of thought went into the design. There were two very interesting aspects.

At that time, almost all PCs used one of two CPUs: the MOS 6502 or the Zilog Z80. Each was the product of a relatively small, upstart company, and each “borrowed” its basic instruction set and much of its design from another, more expensive CPU produced by a larger company — the Motorola 6800 and the Intel 8080 respectively. (To add to the ethical questions, both were largely designed by engineers who had also been involved with the creation of their “inspirations.”) Of more immediate import, both were 8-bit chips capable of addressing only 64 K of memory. This was already becoming a problem. The Apple II, for example, was limited, due to the need to also address 16 K of ROM, to 48 K of RAM at this time. We’ve already seen the hoops that forced Apple and the UCSD team to run through to get UCSD Pascal running on the machine. Even where these CPUs’ limitations weren’t yet a problem, it was clear they were going to be soon. The team therefore decided to go with a next-generation CPU that would make such constraints a thing of the past. IBM had a long history of working with Intel, and so it chose the Intel 8088, a hybrid 8-bit / 16-bit design that could be clocked at up to 5 MHz (far faster than the 6502 or Z80) and, best of all, could address a full 1 MB of memory. The IBM PC would have room to grow that its predecessors lacked.

The other interesting aspect was this much-vaunted idea of an “open architecture.” In Accidental Empires and even more so in Triumph of the Nerds Robert X. Cringely makes it out to be a choice born of necessity, just another symptom of the machine as a whole’s slapdash origins: “An IBM product in a year! Ridiculous! To save time, instead of building a computer from scratch, they would buy components off the shelf and assemble them — what in IBM speak was called ‘open architecture.'” Well, for starters “open architecture” is hardly “IBM speak”; it’s a term used to describe the IBM PC almost everywhere — and probably least of all within IBM. (In his meticulous, technically detailed Byte magazine article “The Creation of the IBM PC,” for example, team-member David J. Bradley doesn’t use it once.) But what do people mean when they talk about “open architecture?” Unfortunately for flip technology journalists, the “openness” or “closedness” of an architecture is not an either/or proposition, but rather, like so much else in life, a continuum. The Apple II, for example, was also a relatively open system in having all those slots Steve Wozniak had battled so hard for (just about the only battle the poor fellow ever won over Steve Jobs), slots which let people take the machine to places its creators had never anticipated and which bear a big part of the responsibility for its remarkable longevity. Like IBM, Apple also published detailed schematics for the Apple II to enable people to take the machine places they never anticipated. The CP/M machines that were very common in business were even more open, being based on a common, well-documented design specification, the S-100 bus, and having plenty of slots themselves. This let them share both hardware and software.

Rather than talking of an open architecture, we might do better to talk of a modular architecture. The IBM would be a sort of computer erector set, a set of interchangeable components that the purchaser could snap together in whatever combination suited her needs and her pocketbook. Right from launch she could choose between a color video card that could do some graphics and play games, or a monochrome card that could display 80 columns of text. She could choose anywhere from 16 K to 256 K of onboard memory; choose one or two floppy drives, or just a cassette drive; etc. Eventually, as third-party companies got into the game and IBM expanded its product line, she would be all but drowned in choices. Most of the individual components were indeed sourced from other companies, and this greatly sped development. Yet using proven, well-understood components has other advantages too, advantages from which would derive the IBM PC’s reputation for stolid reliability.

While sourcing so much equipment from outside vendors was a major departure for IBM, in other ways the IBM PC was a continuation of the company’s normal design philosophy. There was no single, one-size-fits-all IBM mainframe. When you called to say you were interested in buying one of these monsters, IBM sent a rep or two out to your business to discuss your needs, your finances, and your available space with you. Then together you designed the system that would best suit, deciding how much disk storage, how much memory, how many and what kind of tape drives, what printers and terminals and punched-card readers, etc. In this light, the IBM PC was just a continuation of business as usual in miniature. Most other PCs of course offered some of this flexibility. It is nevertheless significant that IBM decided to go all-in for modularity, expandability, or, if we must, openness. Like the CPU choice, it gave the machine room to grow, as hard drives, better video cards, eventually sound cards became available. It’s the key reason that the architecture designed all those years ago remains with us today — in much modified form, of course.

The committee gave Lowe the go-ahead to build the computer. IBM, recognizing itself that its bureaucracy was an impediment to anyone really, you know, getting anything done, had recently come up with a concept it called the Independent Business Unit. The idea was that an IBU would work as a semi-independent entity, freed from the normal bureaucracy, with IBM acting essentially as the venture capitalists. Fortune magazine called the IBU, “How to start your own company without leaving IBM.” Chairman Cary, in a quote that has often been garbled and misattributed, called the IBU IBM’s answer to the question, “How do you make an elephant [IBM] tap dance?” Lowe’s IBU would be code-named Project Chess, and the machine they would create would be code-named the Acorn. (Apparently no one was aware of the British computer company of the same name.) They were given essentially free rein, with one stipulation: the Acorn must be ready to go in just one year.