S-100 tech Summary (was Re: This is new...)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Wed Apr 15 10:50:58 1998

<> S-100s started out with an Intel 8080, then Zilog Z80. That was
<> pretty much the end of the 8-bit version, although there were
<
<Hmmm...this is sort of like the Creationist version of where S-100 came
<from. Actually, a guy named Ed Roberts at a company called MITS that
<built a computer called the Altair 8800 invented the S-100 bus.

It's the of the form... In the beginning Ed created MITS and intel created
the 8080 and it was ok,... :-)

<> The response time compared quite favorably to contemporary low
<> end DEC PDP-11s, and for a fraction of the cost.

Actually the Alpha MicroSystems was a s100 box in the 1979-80 time frame
that used the WD13 chipset (same as the LSI-11/pdp-11) with slightly
different microcode and it did run with the same or slightly better
performance than the LSI-11/03 it's contemporary.

<> Another problem was the unregulated power supply. Unregulated
<> +8 and +/-16VDC was run over the bus itself, right next to
<> signal lines. Every board required it's own regulation, which
<> could take 20% or more of the board space, as well as being a
<> nightmare to keep cool. If you see early pictures of loaded
<> IMSAIs, the cover was always off. This was a necessity, the
<> heat was too much with the cover on. I had to use a 16" fan to
<> keep mine running with 64KB of 2102 based static RAM (not 21L02s
<> BTW, they cost more than the fan did).

Typical of the earlier boxen. Their cooling path was poorly thought out
at best and looking at them it's was obvious. Usually some fish paper
in the right places did the trick.
 
<> >As for laissez-faire, I never have believed in it. It makes society
<> >too concerned about money. This is proven when complete crap hardware
<> >is released now, and people don't care because it's good _financially

An aside to this... some of the S100/SS50/trs80/apple... items from the
various third parties were quite the garbage. Some fo the suppliers were
patently ripoff artists where money was taken and nothing shipped.

Reality check. PCs today can be purchased to do real work and expected
to perform. Computers of the late '70s and into the early 80s were often
useless as shipped if they worked and required a fair amount of acumen to
configure, expand and *required* programming skills. The latter due to
add hardware and even create applications to make them useful.

For example to add a hard disk in 1980 (10mb DISCUS system was $3995.00)
and that was the drive and a s100 card. The user would have to set the
jumpers on the card for the correct IO ports to not conflict with their
system. The system BIOS would have to be rewritten to add the hard disk
and the system tracks on the floppies and the hard disks would have to be
rewritten onto the media. This assumes you had the BIOS for your system
and it was CP/M or similar... all others the bet was off. So to add a
hard disk you needed a system that was up and running, sources, could
read the sources supplied...

I often had the problem of the NS* using hard sectored 5.25 and the
supplied media was 8"!!!

Also you had an assembler, editor, debugger and knew 8080/z80 assembler.
When I went from a teltek controller to a different one... do it all over
again as the new one was totally incompatable. Far cry from an IDE disk
and setting the CMOS.

Allison
Received on Wed Apr 15 1998 - 10:50:58 BST