DoN. Nichols wrote:
On 2007-11-24, Jon Elson wrote:
Another insane project was building a 32-bit bit-slice computer.
The main CPU section was built on two hand-made wire-wrap boards
about 14" square. It had 16 K words of 96-bit wide control
store for the microcode.


Interesting. I remember considering making a Motorola 6800 CPU
from 2-bit bit-slice modules (for a hoped increase in speed), but never
got around to starting that project.

Lots of wire-wrapped things with 6800, 6802 and 6809 CPUs.

Yeesh, that was the Signetics/Intel 3002 series, with their
insane local branching scheme, where your program listing had to
be a 2D grid, with routines writhing all over the map like snakes!

I actually got it running at the
blinding rate of 8 MHz for 2-register operations and 6 MHz for
3-register.


Pretty good for wire-wrapped. I wonder how much it could have
been boosted by more careful design of the routing of the signals?

Not much. This was really old-school Schottky TTL, there was a
limit on how much they could put in one chip without thermal
problems. The registers were external to the ALU chips, and you
had to decode the register addresses. I could have made it un
faster with faster register chips, but they would run even
hotter, and be a lot less capable. The AMD register chips had 3
ports, 2 for reading one for writing, and there wasn't much
alternative. 55 ns access time, I seem to recall, sounded
blindingly fast at the time!

I wrote an emulator in BASIC and a macro assembler
for it, and had a pretty sophisticated (for the time) download
and diagnostic system for it that ran on a Z-80 system with
S-100 bus and PC/M. (Is that the right OS for the old S-100
systems?)


Close -- CP/M.
Yes, of course, how could I have forgotten that. I spent a LOT
of time working with it, even rigged up a VERY early Memorex 10
MB Winchester drive to it, also has a 12" vector-writing CRT
with a light pen, and a Honeywell 600 LPM drum printer, also 800
BPI 9-track mag tape for backup.
I was going to implement a 32-bit microprogrammed
computer with it, based loosely on the IBM System/360, and then
have to adapt an OS to run on it. Well, I got bogged down in
microcode, and never got anywhere NEAR finishing the thing.


An impressive project, anyway.

it would have been impressive if I'd ever gotten it running.
I had 2 MB of Memorex 3rd party static RAM memory out of IBM
370's at work that were scrapped. I was going to build an
interface between that memory and the 32-bit CPU, which would
have allowed me to actually run a program on the thing. But,
the microcoding was a total nightmare, partly because the tools
I had were a bit primitive. It took me a couple days to write
the code to do the simplest operations, like add 2 numbers
together and write the result in another register. The last
thing I did was get a simple 32x32 - 64 bit multiply working.
Next would have been divide, and I think that's about where the
project stopped.

Then, it became possible to buy a DEC MicroVAX-II CPU piece by
piece from brokers, and I never looked back! I still pull out
the huge wire-wrapped boards for visitors to marvel at.


I moved from the Altair 680b to the SWTP 6800, and then the SWTP
6809, (the last finally running with DOS-69 and OS-9 at the flick of a
switch) before I started picking up Sun workstations and servers,
starting with a Sun 2/120, and up through a current pair of Sun Blade
1000s and a Sun Fire 280R.
I got a SGI Iris 2020 off the loading dock at work. It almost
booted up, you could look around in the file system, etc. I got
some help on the net and determined the graphics engine was bad,
and bought all the boards out of a German guy's system for $100.
His graphics engine worked, and the thing came up and ran their
OS and nifty demos like the "flight simulator". It ran for
about 2 years and then the graphics engine blew again. I sold
all the guts for $200 to a broker. This machine was so far
beyond obsolete it wasn't funny. 68020, I think.

My VAX just died this year, after 20 years of operation, and a
number of upgrades. It is also mighty far out of date, 0.9
MIPS, 4 MB of memory. I had one last application running on it
for the last 7 years, an energy/environment monitoring system
that has a couple LCD displays around the house that show time,
inside and outside temp, humidity, etc. and also logs a whole
bunch of info on furnace and air cond operation to a file every
15 seconds. I finally migrated the code and interface over to
my server PC. Every night it summarizes the day's data. Used
to take 3 minutes on the VAX while the displays froze. On the
PC it takes 0.7 seconds, so the clock display never misses a beat.

Jon