The Intel 8080
Microprocessor was introduced in 1974. Shortly
thereafter, the MITS Altair 8800 was introduced as a
microcomputer kit for hobbyist use. The Altair 8800 was a
crude but functional machine, which used toggle switches and
LEDs on the front panel for input and output. The Altair
was an expandable system which included a card cage with a bus
consisting of 100-pin connectors, initially known as the
Altair Bus.
About six months after the Altair was
introduced, the IMSAI
8080 microcomputer appeared on the market. It was
essentially a clone of the Altair with greatly improved
"ergonomic" front panel board and proved more
reliable than the Altair. This machine also used the
100-pin "Altair" bus, which became known as the
S-100 bus.
Later, other S-100 bus-based machines appeared
on the market, and the S-100 bus was updated and standardized
as the IEEE-696 Bus.
My first computer was the Northstar
Horizon S-100 based microcomputer. It lacked the
elegant front panel of the IMSAI, but included a Zilog Z80
processor running at 4MHz. This machine was available in
kit or assembled form, and came with either a metal or walnut
wood top. The most notable contribution of Northstar
computers were the integrated dual 5.25-inch mini-floppy disk
drives. These Northstar floppy disk subsystems were also
available (and many were used) on Altair and IMSAI machines
which lacked integral drives. The Northstar disk
controller was interesting that it was made completely out of
discrete logic (no floppy controller chip) and required the
use of 48-TPI hard-sectored diskettes. These diskettes
have 11 index holes rather than one sector hole found in more
modern soft-sectored diskettes. Later the Northstar
Horizon was available with a 5Mb hard drive in place of the
second floppy drive.
There were many other manufacturers of S-100
based machines. One other S-100 based machine I have in
my collections is the Cromemco
System One. This is a fairly late-model S-100 based
machine, produced in 1982. It has a Cromemco DPU (Dual
CPU) processor card, which contains a Z80 processor as well as
a Motorola MC68000. I'm looking for documentation for
this machine to make available on-line.
I've also included an Altos
5-15AD microcomputer in my collection even though it is
not an S-100-based machine. The Altos 5-15 is basically
a single-board computer with the single-board housed in the
chassis above the floppy drives and power supply. This machine
can run the OASIS
operating system, as well as CP/M-80
and MP/M-II.
This Altos is available on-line using the link below. If
anyone has documentation for this machine in electronic or
hard-copy format, I'd like to obtain a copy to make available
on-line.
