Dawn of the Personal Computer: From Altair to the IBM PC
Mark-8
Radio Electronics and Popular Electronics magazines used to engage in contests of one-upmanship for front-cover projects. In July 1974 Radio Electronics’ cover featured one of the first CPU-based PCs, the Mark-8 minicomputer kit.
For about $50 you got an instruction booklet and a few circuit boards.
After gathering $250 or so in components like RAM chips, resistors, capacitors and the expensive 8008 microprocessor and then doing a whole bunch of soldering the buyer would, hopefully, end up with a real computer running at .5 MHz with 256 bytes of RAM and some basic I/O.
Hobbyists found many ways to expand this system but the 8008’s address limit of 16K ultimately proved a barrier, especially when alternatives existed such as Popular Electronics’ response: the Altair 8800.
RAM 256 bytes to 16K
CPU .5MHz Intel 8008
Supporting OS None
Predecessor None
Successor Various Mark-8 homebrew iterations
Notable Firsts First popular computer kit
MITS Altair 8800
In 1975, responding to Radio Electronics’ Mark-8, Popular Electronics debuted the Altair 8800, an Intel 8080-based machine sold as a 1K kit for $500.
Although the Altair wasn’t really the first PC, what it lacked in primacy it made up for with its ability to generate excitement. A soon-to-be Harvard dropout named Bill Gates was so taken by the machine that he and some friends felt compelled to write a version of BASIC for it. This landed them on the MITS staff and, eventually, led to the founding of “Micro-Soft” - later Microsoft.
The machine also defined the first standard Personal Computer bus architecture, the S-100 bus, and inspired a new generation of personal computing pioneers; the number of companies formed and fortunes made because of the Altair is simply amazing although few of those made it to today.
RAM 256 bytes to 64K
CPU 2 MHz Intel 8080
Supporting OS MITS DOS, CP/M, and others
Predecessor Mark-8 and other early PCs
Successor IMSAI 8080 and all other S-100 machines
Notable Firsts First S-100 bus machine, first widely popular PC
KIM-1
The KIM-1 was designed to showcase the new MOS 6502 microprocessor. The chip was introduced at $25 per unit when the cost of Intel’s 8080 was nearly $200 in bulk. In spite of the price, the 6502 was for real, as the KIM-1 proved.
MOS was quickly bought up by Commodore who used the chip in their Commodore PET line of computers.
A couple of guys named Steve quickly built a single-board computer using the new chip and then named it after a fruit. Over time, it was incorporated into machines from Atari, Ohio Scientific and more.
The 6510, a later version in the 6502 family, powered the popular Commodore 64.
RAM 1K
CPU 1 MHz 6502
Supporting OS None
Predecessor None
Successor All other 6502-based machines (Apple, Commodore, Atari, etc.)
Notable Firsts First use of the 6502 computer