Encyclopedia
The
MITS Altair 8800 was a
microcomputer design from 1975, based on the
Intel 8080A CPU. Sold as a kit through
Popular Electronics was started by Ziff-Davis [i] in October 1954 as a magazine for students and exp ...
magazine, the designers intended to sell only a few hundred to hobbyists, and were surprised when they sold over ten times that many in the first month. Today the Altair is widely recognized as the spark that led to the
personal computer revolution of the next few years: The computer bus designed for the Altair was to become a de facto standard in form of the S-100 bus, and the first programming language for the machine was
Microsoft's founding product, Altair BASIC.
History
While serving at the
Air Force Weapons Laboratory at
Kirtland Air Force base, New Mexico, Ed Roberts and Forrest M. Mims III decided to use their electronics background to produce small kits for
model rocket hobbyists. Roberts and Mims, along with Stan Cagle and Robert Zaller, founded
Micro Instrumentation and Telemetry Systems in Roberts' garage in
Albuquerque, New Mexico, and started selling
radio transmitters and instruments for
model rockets.
In 1969 Roberts bought out the others and moved to a larger office, where he manufactured
calculator kits for hobbyists. Mims assisted by writing manuals for some of the products in return for kits. In 1972,
Texas Instruments developed their own calculator chip and started selling complete calculators at more than half the going rate. MITS was devastated by this, as were many other companies, and Roberts struggled to reduce his quarter-million dollar debt.
With the release of the first 8-bit microprocessor, the
Intel 8008, in 1972, and the more powerful 8080 in 1974, a number of hobbyists started designing microcomputer kits. In July 1974, one such design, Jonathan Titus' well thought-out
Mark-8, based on the 8008, was advertised in
Radio-Electronics magazine was published under various titles from 1929 to 2002....
magazine. The design was purely on paper, requiring the builder to track down the parts one at a time, a task that was basically impossible outside of
California. Although the Mark-8 was not a success, the editors at
Popular Electronics realized that someone was going to be the first to deliver a "real" kit, and decided they wanted to do it. At this point the story becomes somewhat less clear.
The design
Roberts looked for a deal on
CPUs, and eventually talked
Intel into supplying him with cosmetically blemished 8080's for $75, when they normally sold for $360. In fact the deal wasn't quite as shrewd as Roberts thought at the time; Intel chose the $360 price simply as a play on the famous
IBM System/360 mainframe. The name finally decided upon for the computer came from Solomon's 12-year-old daughter, Lauren. She suggested
Altair, which was the destination for the Starship Enterprise during an episode of
Star Trek that she was watching.
The first working sample was immediately shipped, by train, to
New York. However, it never arrived due to a strike by the shipping company. The first example of this groundbreaking machine is thus lost to history. Solomon had already taken a number of pictures of the machine and wrote the article based on them, while Roberts got to work on building a replacement. Everything came together, and the kit was officially available on December 19, 1974.
The launch
The kit was first announced in the January 1975 edition of
Popular Electronics was started by Ziff-Davis [i] in October 1954 as a magazine for students and exp ...
.
The timing seemed to be just right. The electronics hobbyists were moving on to computers as more and more electronics turned digital, and yet they were frustrated by the low power and flexibility of the few kits that were already on the market. The Altair had enough power to be actually useful, and was designed around an expandable system that opened it up to all sorts of experiments. Roberts needed to sell 200 over the next year to break even, but instead received thousands of orders in the first month, including 200 in one day.
Within only six months competition arrived in the form of the
IMSAI 8080, which included a keyboard, monitor and a
floppy disk controller. Roberts was furious, and spent an increasing amount of his time trying to "knock off" these competitors instead of improving the Altair. By 1976 there were a number of much better built machines on the market, and when Roberts started demanding the newly-appearing computers stores sell only Altair machines, they instead turned to the competition and in a turn of irony MITS was quickly squeezed out of the market they themselves had created.
Description
In the first design of the Altair, the parts needed to make a complete machine would not fit on a single
motherboard, and the machine consisted of four boards stacked on top of each other with stand-offs. Another problem facing Roberts was that the parts needed to make a truly useful computer weren't available, or wouldn't be designed in time for the January launch date. So during the construction of the second model, he decided to build most of the machine on removable cards, reducing the
motherboard to nothing more than an interconnect between the cards, a backplane. The basic machine consisted of five cards, including the
CPU on one and memory on another. He then looked for a cheap source of connectors, and came across a supply of 100-pin
edge connectors. The rest, as they say, is history, and the S-100 bus was eventually acknowledged by the professional computer community and adopted as the IEEE-696 computer bus standard.
For all intents, the Altair bus consists of the pins of the
Intel 8080 run out onto the backplane. No particular level of thought went into the design, which led to such disasters as various power lines of differing voltages being located next to each other, leading to easy shorting. Another oddity was that the system included two unidirectional 8-bit data buses, but only a single bidirectional 16-bit address bus. A deal on power supplies led to the use of +8
V and +18V, which had to be "pulled down" on the cards to
TTL or RS-232 standard voltage levels.
The Altair shipped in a two-piece case. The backplane and power supply were mounted on a base plate, along with the front and rear of the box. The "lid" was shaped like a C, forming the top, left and right sides of the box. The
face plate, reportedly inspired by the
Data General Nova minicomputer, included a number of large
toggle switches to feed
binary data directly into the memory of the machine, and a number of red
LEDs to read those values back out.
Programming the Altair was an extremely tedious process where one toggled the switches to positions corresponding to an 8080 opcode, then used a special switch to enter the code into the machine's memory, and then repeated this step until all the opcodes of a presumably complete and correct program was in place. When the machine first shipped the switches and lights were the only interface, and all one could do with the machine was make programs to make the lights blink. Nevertheless, many were sold in this form. Roberts was already hard at work on additional cards, including a
paper tape reader for storage, additional
RAM cards, and a RS-232 interface to connect to a proper
terminal.
Software
Altair BASIC
Around this time Roberts received a letter from a
Seattle company asking if he would be interested in selling their
BASIC programming language for the machine. He called the company and reached a private home, where no one had heard of anything like BASIC. In fact the letter had been sent by
Bill Gates and
Paul Allen from the
Boston area, and they had no BASIC to offer. When they called Roberts to follow up on the letter he expressed his interest, and the two started work on their BASIC interpreter using a self-made
simulator for the 8080 on a
PDP-10 minicomputer. They figured they had 30 days before someone else beat them to the punch, and once they had a version working on the simulator, Allen flew to Albuquerque to deliver the program, Altair BASIC , on a
paper tape. Miraculously it worked the first time, and Gates soon joined him and formed
Microsoft, then spelled "Micro-Soft".
The Altair 8800 in popular culture
The Altair 8800 appeared in an episode of
Malcolm in the Middle was an American situation comedy [i] created by Linwood Boomer [i] for the Fox Network [i] ...
. When Reese and Malcolm dig through some junk in the garage, Malcolm finds an Altair 8800. Reese insists that it is trash, but Malcolm recognizes the value and offers to sell it to his mother's colleague, Craig, for $1300. However, when Malcolm tried to sell it in front of Lois, who suddenly realizes it is worth more than $1000, Reese throws it on the ground and stomps it to pieces, bringing Lois to tears.
Emulators
- SIMH emulates Altair 8800 with both 8080 and Z80.
External links
