IMSAI - History
was founded by an ex IBM employee, William Mallard, as a business called IMS
Associates, Inc., in 1973. It was located in San Leandro CA. IMS stood for
Industrial Micro Systems. They did contract hardware/software work for business
and the government. One project they had was the development of a
"Hypercube" -- a multiprocessor 8080 CPU system allowing parallel processing. As
the project evolved they needed a disk operating system (hardware and software).
Apparently they had difficulties with a CDC hard disk system and looked into
developing a CP/M based system (then new) on an Altair computer. They were
unsuccessful in working out an arrangement with Altair and so Joe Killian their
chief engineer decided to build an Altair clone. They quickly found that
there was interest and demand from computer hobbyists for such a system. In 1975
they made a name for themselves by providing a much better constructed "S-100"
system utilizing sound engineering designs they had learned from the work above.
The company took off.
To finance rapidly growing operations,
IMSAI pledged 20% of its stock as convertible note in exchange for $250,000 from
the investment firm Marriner & Co. In 1976, in partnership with
others IMS launched a successful computer reseller franchise ComputerLand.
In 1982, ComputerLand's sales reached over $400 million and by 1984 the venture
reached over $1 billion in revenue. However legal troubles from the failure of
IMS, centered largely on a convertible note from the Marriner partnership that
was later sold to a group of investors, led to a lawsuit in which Millard lost a
substantial portion of his stake in ComputerLand. In the late 1980's Millard
relinquished control of ComputerLand. In 1987, he sold ComputerLand to E.M.
Warburg, Pincus & Co. for about $200 million. Apparently there were
serious management problems at IMSAI almost from the beginning with large
salary discrepancies between executives and staff compounded with unrealistic
tasks and goals. In spite of its early start in the business it quickly lost out
to other competing companies. Nevertheless the IMSAI 8080 box to
this day probably represents the image most associated with the S-100 bus. Over
15,000 of them were manufactured. Working systems on eBay have reached over
$3000. The rights to the IMSAI name, materials, documentation etc have
been obtained by a guy named Todd Fischer who started a company called
Fischer-Freitas Company. He has a web site at
where he describes an IMSAI Series II. This is a S-100
bus/IBM-PC proto-type hybrid. Todd unfortunately is seriously ill -- we
wish him well.
the main competition IMSAI had was Altair. The IMSAI was a superior
machine in almost every respect from a hardware perspective. For example The
Altair used a power supply rated at 8-amps and constructed of radio grade
components. This was thought to be more than adequate for the original design of
the computer, but not for an expanded system. The
IMSAI power supply, on
the other hand, came equipped with a massive transformer and very large
computer-grade capacitors. The standard model was rated at 20 amps. This big
power supply could deliver 30 amps at 5 volts and 3 amps at + - 16 volts. Having
a large power supply was an advantage because all the S-100 Bus computers used
un-regulated power supplies with power regulators located on each individual
circuit board. One of the most common causes of failure in S-100 computers was
failure of the on-board power regulators. The use of massive transformers and
capacitors provided less electrical fluctuation and longer life for these power
regulators. The product brochure for this system can be seen
One most important thing the Altair had
over IMSAI was the BASIC interpreter written by Bill Gates of Microsoft.
IMSAI had little software capability initially. The only software they supplied was a
modified version of a software package, written for Processor Technology and
placed in the public domain. This was delivered on a paper tape and required 8K
of memory. The software consisted of a executive program, including a text
editor and an assembler program for assembly language. To use it, you had to
have a teletype tape reader. Hardly the type of thing a non-computer hobbyist
would use. IMSAI promised for months they would come out with their own BASIS.
People got fed up waiting. Altair BASIC soon became the standard language
for personal computers even before Microsoft got out of its restrictive
agreement with Altair. In their favor however they early on appreciated
the use of a disk operating system and quickly adapted CP/M for their system.
One advantage they had however was the fact that
almost all S-100 systems were not "pure". Most had a mixture of different
manufactured S-100 boards. IMSAI sold many of their boards for use in non IMSAI
systems. The company died a slow death by funds being drawn out of the
operation to fund the ComputerLand franchise operation. They came out with
a "all in one" box called the VDP-80. It looked great on the outside but was
unreliable internally. It utilized the infamous Persci 8" floppy drives. The
company never really recovered. The company closed down in October 1979 with
some of the assets being sold to
Fulcrum the rest to the company called Fischer-Freitas mentioned above.
IMSAI S-100 Boards
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