Dawn of the Personal Computer: From Altair to the IBM PC
IBM PC/AT
The PC/AT introduction was the last time IBM managed to set the PC pace. Its Intel 80286 processor was a true 16 bit unit which meant that IBM had to redesign the bus for 16 bit addressing. The bus quickly became the industry standard and was soon named as such.
The ‘286 also upped RAM limits from 1MB to 16MB and brought about new levels of suffering with Expanded and Extended memory management.
Over-clocking was briefly possible with the earliest ATs until IBM redid the ROMs to prevent that. Other vendors, however, were more accommodating.
Either way the AT brought forth enough power for Microsoft to run a new DOS shell with technology borrowed from Xerox PARC.
And thus Windows was born.
RAM 256K-16MB
CPU 6MHz 80286
Supporting Operating Systems IBM PC DOS, CP/M and others
Predecessor IBM PC XT
Successor IBM PS/2 line
Notable Firsts First IBM 16 bit PC and Bus
A look back at these old machines shows the clear path of Moore’s Law. Since the release of the IBM PC/AT, the personal computer has grown faster and microchips have shrunken smaller by orders of magnitude. The antiques we’ve showcased may be considered slow and crude by today’s standards but they all contributed, even if only a little, to the PCs we use today.
Early Media

In the early days of personal computing, users had any number of options for loading programs and for keeping their data safe. Floppy and hard disks were common, but so was paper tape and cassette tape. Less common were micro-cassette tape, bubble memory, and even “floppy ROMs,” which were thin, plastic records sent with some computer magazines. And speaking of ROMs, there were the standard ROM chips plugged into boards but many manufacturers put them into card-edge packages and tucked them into plastic cases (cartridges.)
Magnetic Media
Examples: 5.25” 30 MB hard drive, 8” floppy, 5.25” floppy, 3.5” floppy, Coleco Adam High Speed Digital Data Pack, Cassette Tape, Micro Cassette Tape.
All of these and more were used on early computers. Most were slow and fairly clunky, but they were far better than re-keying programs every time you rebooted.
The total capacity of these represents less than 1/20th of one CD ROM.
Solid State Media
Examples: 2K ROMs, ROM Board/bare Exidy Cartridge, Atari Cartridge, Commodore 64 Cartridge, TI 99/4a Cartridge, Intel 1702 EPROM (256 bytes), Exidy Sorcerer Cartridge (in a hollowed out 8-track tape case) Coleco Adam/Colecovision cartridge.
Cartridges and ROMs were used to provide ready code at boot so that the computer was useful as soon as power was applied.
Analog Media
Examples: Paper tape, Interface Age Floppy ROM, Punched cards.
Paper tape was widely popular for the earliest computers due to the easy availability of used Teletypes. These operated at 110 baud (10 bytes per second) which meant that a typical 8K program would take nearly 15 minutes to load! Most other media were faster, but not always by much.
Bill Gates Asks Hobbyists to Pay Up
Early users groups from coast to coast (the SiliconValley Homebrew Computer Club being the most famous) were venues for geeks to gather, demonstrate their knowledge, and share their inventions. Some folks demonstrated their new computers, some shared renditions of old tunes played on an Altair computer, and some shared software. Sometimes it was software they wrote and sometimes it was software that someone else wrote.
In one notable early incident, a regular at the Homebrew Computer Club obtained a copy of Altair BASIC on paper tape. Prior to the next meeting he made dozens and dozens of copies, which he freely distributed to other attendees.
So, in 1976 Bill Gates had a problem. He was making software that everyone loved but that few were bothering to pay for. In frustration, Gates penned an “Open Letter to Computer Hobbyists,” which was published in the Homebrew Computer Club newsletter and elsewhere. In the missive he explained that the unauthorized copying of software was theft and that doing so inherently discouraged developers from producing good software.
He explained that only about 10 percent of Altair owners had bought BASIC (although all seemed to own it) and that he and his staff were effectively working for $2 an hour producing quality software that the hobbyist community clearly valued.
The letter sparked some harsh exchanges, including a more pointed follow-up letter by Bill Gates, and ultimately started the discussion about software piracy. This discussion has, of course, picked up steam and continues to this day.