Original URL: http://www.theregister.co.uk/2011/08/12/ibm_pc_30_anniversary/

The IBM PC is 30

On 12 August 1981, the world changed

By Tony Smith

Posted in Vintage, 12th August 2011 06:00 GMT

IBM announced its new machine, the 5150, on 12 August 1981. It was no ordinary launch: the 5150 wasn't the 'big iron' typical of Big Blue - it was a personal computer.

Here's the original 1981 announcement (PDF).


IBM's Personal Computer: the 5150
Source: IBM

IBM came late to the party. Through the 1960s and 1970s, it had focused on corporate computing: expensive mainframe and, later, mini computers. But by the end of the 1970s, it had seen the likes of Tandy's TRS-80, Commodore's Pet and Apple's Apple II win support from smaller businesses, individuals and even in some of the big companies IBM traditionally targetted.

IBM bosses realised there was clear demand for a single-user system, and while their emphasis on big machines would continue, it was clear that the personal computer was an opportunity open for exploitation.

The 5150 - the machine that would eventually be called, simply, the IBM PC, was developed by what was at that time a little known part of the company, the Entry Systems Division, based in Boca Raton, Florida.


IBM advertises its latest personal computer

A 12-strong team was assembled under Don Estridge, the Development Director of the project, codenamed 'Chess'. Lewis Eggebrecht was brought on board as Chief Designer.

Rather than create the 5150 from scratch, Estridge's engineers used existing parts from a variety of other companies, seemingly in marked contrast with IBM tradition. The company made a virtue out of the fact that it made the components used in its machines. When you bought an IBM computer, it had IBM's imprimatur of quality through and through.

IBM PC Specs

IBM's PC predecessors

It has been claimed that the Chess' team's off-the-shelf approach was mandated by the limited development resources they were allowed, a sign that senior IBM executives saw no real future in the PC. Possibly so, and there were certainly time pressures: IBM management wanted the machine ready quickly, and Estridge and co appear to have been given a year to design the machine.

IBM Scamp

IBM's Scamp prototype
Source: Murple.net

But this was an approach IBM had taken before. In 1973, its General Systems Divison (GSD) embarked on 'Project Scamp', an effort to develop a single-user machine. Scamp stood for "Special Computer, APL Machine Portable" - the outcome was essentially a mobile personal computer-cum-calulator designed to run pre-loaded applications and allow user to write their own software using the APL language.

The Scamp team was given six-months in which to come up with a prototype. Ultimately, the result was the IBM 5100, a (barely) portable machine that weighted 23kg, had 16-64KB of storage depending on model, priced between $8975 and $19,975. It debuted in September 1975.

IBM 5100

Scamp follower: the IBM 5100
Source: Wikepedia

GSD maintained its interest in personal computer and, in July 1981, announced the System/23 Datamaster, a more PC-like machine than the 5100, but one still aimed at big business rather than individuals. The $9000 Datamaster was an all-in-one machine complete with keyboard, CRT display, 8-bit Intel 8085 processor and two 8in floppy disk drives.

The team at GSD developed the Datamaster using off-the-shelf components, most notably the Intel CPU. This choice seems to have influenced the Chess team, who eventually selected the 8088. They were familiar with the Datamaster endeavour: the 5150 would use the same expansion bus and add-in card slots as the GSD machine.

IBM System/23 Datamaster

The might-have-been PC: IBM's System/23 Datamaster
Source: Oldcomputers.net

The 5150's 8088 CPU was clocked at 4.77MHz and could be augmented with an optional 8087 maths co-processor. It had 16KB of memory and a 5.25in floppy drive - some models had two - for storage.

OS Stories

The mythology of the IBM PC's operating system has it that the company approached Digital Research (DR), creator of the CP/M OS, but found it lacking in enthusiasm for the project. Microsoft's Bill Gates got wind of this and pitched MS-DOS instead.

MS-DOS Advert

Microsoft advertises DOS in 1983
Source: Fraggle UK at Flickr

In fact, it's likely IBM selected CP/M-86 but was forced to look, at least temporarily, elsewhere as DR's effort to port CP/M to the Intel 8086/8088 CPU was taking longer than planned. Gates may well have pitched an alternative - IBM was already talking to Microsoft about using the latter's implementation of the Basic programming language - and appears to have won the deal in November 1980.

Not long after, Microsoft licensed 86-DOS from Seattle Computer Products (SCP), specifically to sub-license the OS to IBM in turn. 86-DOS had been created by SCP as a stand-in for CP/M-86 and was thus intentionally compatible with the DR OS.

IBM agreed to use 86-DOS, which in July 1981 was acquired in its entirety by Microsoft and renamed MS-DOS. IBM would bundle it as PC-DOS.


Not just for grown-ups

At launch, IBM said it would offer CP/M-86 for the 5150. "IBM has contracted with Digital Research... to make CP/M-86... available for the IBM Personal Computer," the company said on the 5150's day of launch. "We expect [its] availability will provide the opportunity for many current applications to be transferred to the IBM Personal Computer with minimal modifications."

Send in the clones

For many users, MS-DOS was sufficient, and the operating system became the standard, helped by Microsoft's entrepreneurial willingness to license MS-DOS to other hardware manufacturers. They, noting the stamp of authority the IBM brand had now placed on personal computing, were quick to emulate its offering, an approach made easier by the Chess team's use of third-party components.

The PC's Bios belonged to IBM, but clever coders worked to produce their own Bios implementations that, to the host OS and applications, would be indistinguishable from Big Blue's own.

Columbia Data Products

Columbia Data Products' 384
Source: MyNewOffice

Third-party Bioses, IBM's open hardware architecture and Microsoft's willingess to license MS-DOS made cloning an easier route to market than developing a machine from scratch. This serendipitous circumstance shifted the market IBM-ward and would quickly define personal computing's first de facto standard.

Columbia Data Products, introduced the first IBM-compatible computer in June 1982. The following November, Compaq announced the Compaq Portable, the first carry-around IBM clone, though the machine wouldn't ship until March 1983.

By which time, IBM was pushing its machine forward. That month, it introduced the XT - aka the 5160 - a 5150 with a built-in hard drive. Variants of the 5160 followed in October and, a month later, IBM introduced the ill-fated PCjr. It flopped, but February 1984's IBM PC Portable and the August-announced PC AT - aka the 5170, with a faster, 6MHz CPU - increased the PC's customer base even further.

Compaq Portable

The Compaq Portable
Source: OldComputers.net

The 6MHz IBM PC XT 286 debuted in 1986 - a year before the original 5150 was finally discontinued - and the series would go on to adopt each new generation of Intel processor, newer versions of MS-DOS and Windows. By now, though, IBM was just one manufacturer among many and its standing had been supplanted by Microsoft and Intel.

'PC' was now a generic term for machines using a Microsoft OS and an Intel processor.

IBM would go on to create the hugely popular ThinkPad line of notebook computers, launching the first in October 1992. The near total commoditisation of desktop and laptop personal computers persuaded IBM to exit this now low-margin business, and in 2005 it sold the whole lot to China's Lenovo. ®