The
Kim-1 single board microcomputer
The Kim-1 single board computer was
introduced in 1976 by MOS Technology. The first ad appeared in Byte
magazine in April, and it was an instant success.
The Kim-1 was based on the MOS6502
processor, which was similar to the Motorola 6800 and with a nearly
identical pin-out. This was no coincidence as the 6502 was designed by a
former Motorola engineer named Chuck Peddle, the same man responsible for
the 6800. The 6502 was a re-design of the MOS6501, which was a clone of
the 6800, but had static rather than dynamic core--useful for things like
pausing or single stepping the processor. Motorola sued MOS over this, and
MOS discontinued the 6501 out of fear of the giant. The 6502 was the
answer, with a re-designed instruction set and a few hardware improvements
like a built-in clock source. The difference was enough to avoid the whole
Motorola thing. Another major difference was price, The MOS6502 debuted at
about $20 when other processors, like the 6800 and the 8080, were in the
$200 range.
The Kim-1 Gained an almost immediate
following because it was cheap, fully assembled, and contained a large
operating system in ROM. The operating system allowed users to connect the
Kim-1 directly to a Teletype such as the ASR-33, or to a terminal such as
the ADM-3 with nothing more than a few wires. It also contained a fully on
board implemented cassette load and save interface. Kim-1 users could do
more in a few minutes with under $300 than an Altair user could in an hour
for three times the price. (Of course, Altair users were doing it a year
sooner!!)
When introduced, and up until chips with date codes from the 26th week
of 1976, the 6502 contained internal errors. This prevented correct
operation of the ROR command and one of the jump commands. This also
effected the operation of the Kim-1, preventing the cassette ...or was it
the TTY?... code from working properly. I have never tested which routine
fails.
MOS Technology was purchased by Commodore not too long after the
introduction of the Kim, and as a result, the prized "MOS"
version became considerably more rare. Mine is an early MOS version, with
chip date codes ranging from the 15th to the 24th week of 1976.
I use my Kim-1 as a wall clock, running a program from a listing in
Kilobaud Magazine, February 1977, page 80. The full listing is provided
below for those who may have a Kim-1 and wish to give it a try.
I removed my Kim-1 from a cabinet that housed a dual 8" floppy
drive system complete with keyboard and video. I like it best as it is
now: mounted in a frame of my own making, with a vintage switching supply
and battery backup. The Kim-1 hangs on the wall of my family room, where I
keep several of my other old machines. It never fails to draw attention
from guests.
Check out the documentation links below!!