Dawn of the Personal Computer: From Altair to the IBM PC
IMSAI 8080

With the overnight success of the MITS Altair 8800, others quickly geared up to tap into the market. IMS Associates Incorporated (IMSAI) quickly reengineered a pre-production machine to conform to the new S-100 standard while simultaneously fixing a number of obvious flaws in the MITS design.
The result was the IMSAI 8080; the first Personal Computer clone and a movie star to boot.
The IMSAI 8080 conformed to the Altair’s standards while upgrading the front panel, case and power supply with far more robust parts.
In the end the IMSAI outsold and outlasted the Altair; proving that you don’t have to be first to succeed.
RAM 1K-64K
CPU Intel 8080
Supporting OS IMSAI DOS, CP/M, and others
Predecessor Altair 8800
Successor Later S-100 systems
Notable firsts First S-100 clone
Apple I
In 1976 Steves Jobs and Wozniak were both active in the tight-knit Silicon Valley computer hobbyist scene. Inspired by what they saw at various Homebrew Computer Club meetings, they sold their toys (a calculator and a van) for the capital to hand-build the earliest Apples, launching an industry icon.
The Apple I wasn’t particularly revolutionary but it was very well engineered, included video circuitry and it was relatively inexpensive which helped it catch on.
The first run of 200 or so units sold out quickly (at $666.66 apiece) and convinced Apple to build and sell the Apple ][ which, with a little bit of help from the first “Killer App,” revolutionized the Personal Computer market.
RAM 4K
CPU 1MHz 6502
Supporting OS Cassette BASIC
Predecessor KIM-1 and early 6502 systems
Successor Later Apple systems
Notable firsts Apple’s first computer
Sol-20
Until the Sol-20 hit the scene, a personal computer was pretty impersonal. The best a user could hope for was rows of switches and lights or a hex keypad and a handful of LEDs.
It took a lot of work to make those machines do things which meant that they were reserved for only the geekiest of users.
Lee Felsenstein, the yardstick-wielding moderator of Homebrew Computer Club meetings changed that with his S-100 based Sol-20. This machine, sold as a kit or fully assembled, was the first “out of the box” PC, sporting a keyboard, video circuitry as well as ROM based software available at power-up.
When plugged into a TV set (with an RF Modulator) or an inexpensive monitor it was ready to go.
RAM 4K-64K
CPU 2MHz Intel 8080
Supporting OS SOLOS, CP/M, Northstar DOS, and others
Predecessor Altair 8800
Successor Other integrated computers (Apple, Commodore, etc.)
Notable firsts First integrated machine with keyboard, video, etc.
Commodore Pet 2001
The $600 Commodore PET was the first fully integrated “appliance computer” that included everything needed out of the box.
It was effectively an expansion of the earlier KIM-1 with video logic added to drive the internal monitor.
The PET was a popular machine, especially in the educational market, possibly because it was built into an amazingly sturdy steel case.
The system was also attractively designed although some of that came at the expense of functionality. One early complaint was the chicklet-style keyboard (designed to use Commodore calculator keys) which was a far cry from the full-size keyboards included with the PET’s competitors. The original issue of 8K (a 4K model was quickly dropped) of included RAM was also a problem.
These deficiencies, as well as others, were addressed with later updates and helped the Commodore PET line attain high levels of popularity in the US as well as in Europe.
RAM 8K
CPU 1MHz MOS 6502
Supporting OS Built-in BASIC
Predecessor KIM-1
Successor Other Commodore machines
Notable firsts First fully integrated “appliance” computer