Altair 8800

  • U.S. $ 395 kit
  • 495 U.S. $ Fertiggerät
  • Expandable to 64 KB

The Altair 8800 was one of the first home computers. 1974 computer by Ed Roberts and his company Micro Instrumentation and Telemetry Systems ( MITS ) was developed and launched in 1975 for 395 dollars as a kit through advertisements in Popular Electronics, Radio - Electronics and other Hobbyistenzeitschriften on the market. The finished unit cost U.S. $ 495, according to today's purchasing power about 2,200 U.S. dollars.

  • 2.1 S-100 bus
  • 2.2 models
  • 2.3 Operation


During his military service in the weapons laboratories of the United States Air Force base in Kirtland (New Mexico) decided to Ed Roberts and Forrest M. Mims III, to use their electronic background knowledge and to produce small rocket model kits for hobbyists. To this end they founded along with Stan Cagle and Robert Zaller, the company Micro Instrumentation and Telemetry Systems MITS short, in Roberts Garage in Albuquerque and began, radio transmitters and instruments for model rockets for sale.

1969 Roberts bought the shares of the other and rented a bigger office, where he established Calculator kits. Mims helped him, in which he wrote manuals for some of the kits, in exchange, he received kits. 1972 but developed its own chip for Texas Instruments calculator and began to complete calculator for slightly more than half of the then fair market value to sell. MITS and many other companies have been virtually destroyed by this circumstance, and now Roberts had problems to repay its debt of half a million U.S. dollars.

With the introduction of the Intel 8008 in 1972 and the improved successor to 8080 in 1974 began some hobbyists to design microcomputer kits. In July 1974, the Mark- 8 was advertised in Radio - Electronics. The kit was sold only in the form of plans on paper, and although it was not a commercial success ( or perhaps because ) it prompted the editors of Popular Electronics to first sell a complete kit. At this time, the further course of the story is unclear.

The construction

Roberts was looking for a good business for the CPU and Intel finally brought to him 8080 CPUs that were cosmetically damaged, at $ 75 instead of the normal (though to be understood only as a symbolic allusion to IBM's System/360-Mainframe ) price from 360 U.S. dollars to sell.

Next, a name for the yet-unnamed kit had to be found; Roberts struck in honor of Popular Electronics before the name PE -8. Les Solomon, the technical manager at Popular Electronics, but was looking for a more memorable name. What he should tell later that he had asked his daughter while ( just a series of Star Trek was looking at ), as the computer name on the Enterprise. This had no name, but the crew of Captain Kirk flew straight to the Altair.

The introduction

The first working model was shipped immediately to New York to Popular Electronics. Due to a strike at the transport company that instance but never arrived and has been missing ever since. However, Solomon had already made photos from Altair and wrote the article now based on the photos while Roberts immediately built a second copy. The kit was made ​​officially available on 19 December 1974.

The kit was presented in January 1975 in Popular Electronics. As more and more electronics are digital, the hobbyists of the time turned to the computer, but were dissatisfied with the skills and the flexibility of a computer kits available at that time. The Altair had these drawbacks and did not have the potential to be really useful. He has also been designed for extensibility, enabling all sorts of experiments. Roberts had 200 kits sell in the first year to reach the breakeven point - instead, met on the first day, a 200 orders and increased to several thousand in the first month.

After only eleven months appeared on the market in the first competition in the form of IMSAI 8080 ( sales start December 16, 1975 ), who possessed also has a keyboard, monitor and a floppy disk controller. Roberts was upset and always spent more time trying to oust competing companies, instead of improving the Altair. 1976, finally, a number of kits available that were the Altair advance, and when Roberts demanded by the emerging computer stores, only the Altair for sale, this competition turned to. So MITS was thrown out of the market, which they had themselves created.

End of production

On 22 May 1977, the Pertec Computer Corporation, a much larger manufacturer of disk drives, MITS buys. The Altair was taken thereupon by the market. Since MIPS did not have the rights to Altair BASIC and this has now been marketed under the label of Micro -Soft, there was later a dispute between the Pertec Computer Corporation and Microsoft.


The lost prototype consisted of four cards that were stacked. The components for the entire computer did not fit on a single motherboard. Another problem was that many parts to make the Altair ever really useful, did not exist or would not be done yet developed to the idea.

Therefore, Roberts decided when designing the kit, build the computer on removable cards and the motherboard so on not more than one connection between two boards to reduce ( backplane). The basic model consisted of five boards, including one for the CPU (2 MHz Intel 8080 ) and one for the memory ( 256 bytes, expandable to 64 KB). Later, there was an additional card mass storage, input / output devices ( inter alia, an RS -232 interface) and memory upgrade.

S-100 bus

Then still had a convenient plug connection will be found - Roberts took this in the edge connector with 100 pins. He called the whole thing the S-100 bus. The S - 100 was recognized by the computer professional community and as the first in the industry standard under the IEEE standard number 696 bus system. He was also the basis of other competing microcomputer (eg IMSAI, SOL, Cromemco ) and about until 1985 used.

Basically this bus was not performed but the pins of the CPU to the backplane. The structure was not well thought out; so many power lines were performed with different voltages to each other, what shorts favored. Another curiosity of the system was that it had two unidirectional 8 -bit wide data buses, but only a bi-directional 16-bit wide address bus. Also a power supply were used for reasons of cost, the traditional electrical voltages of 8 and 15 volts, which had to be turned down on the cards to the standard voltages from TTL ( 5 V) and RS -232 ( 12 V).


Next displaced variants were:

  • Altair 8800a: The shoring was another network device, with a Busspanung of 15 volts and a current of 500 mAmpere. The computer had other toggle switch and a fan.
  • Altair 8800b: Yet another power supply unit supplied the bus with 18 volts and 2 amps. The appearance of the front panel has been changed.


The device itself did not have the usual peripherals today, not even a keyboard. The front panel had LEDs for display of address and data lines, and toggle switches for bitwise programming (see also machine console). Use of Altair BASIC or CP / M as a command-line operating system, a text terminal or a teletype had to be connected via the RS- 232 interface.