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Last modified on 9 November 2013, at 15:39

Altair 8800

The Altair 8800 was an American 8080-based microcomputer introduced in 1975 that is considered the first widely popular home computer. It was sold in kit form and fully assembled and had a characteristic front panel with LEDs. The Altair mainboard had no ICs at all, just S-100 bus (100-pin) edge connectors, so e.g. the CPU and memory were on separate cards.

In the beginning, an Altair was usually controlled via a 110-baud teletype (usually with a punched tape reader and punch for saving and loading data). Later there were also 8" disk drive adapter cards and graphics cards that could show color graphics on a screen.

The Altair could be programmed via its front panel (16 address LEDs and 8 data LEDs and accompanying toggle switches). To load e.g. CP/M from disk, one had to set the program counter to the disk ROM address. One can also use the front panel to key in a small boot loader that will load a program (e.g. a BASIC interpreter) from a connected serial terminal or teletype.

The IMSAI 8080 (prominently featured in the movie WarGames) was an Altair clone that existed back the day.

An original Altair 8800 is worth thousands of dollars today, so there are several clones by hobbyists:

  • "Altair Kit", a real clone with a working S-100 bus and the same ICs (http://www.altairkit.com/)
  • "Altair Clone", which despite its name uses emulation/simulation on modern hardware which is part of the front panel, so the rest is mostly just an empty case (http://altairclone.com/)

The SIMH emulator can also emulate an 8800.

The Altair 8800 started the dominance of 8080/Z80-based, CP/M-supporting microcomputers for the home market, which led to Amstrad including CP/M support in CPCs with disc drives and PCWs (although in 1985 CP/M use was already on the decline). And of course even the Commodore 128 that came out in 1985 could run CP/M thanks to a built-in Z80, so evidently it was not just Amstrad who were lusting after the huge CP/M software library, in particular business software.

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