bit slice chips (was Re: Harris H800 Computer)

[Jon Elson]

I built a 32-bit micro-engine for a project that was 
eventually going to be an IBM 360-line CPU.
I pieced the 360, not because it was the greatest design, 
but it was VERY well laid-out and would be easy to write 
efficient microcode for.  I used the 2903 with 2910 
controller.  I was able to get it to run at 8 MHz, with 
3-address operations running at 6 MHz.

But, the project got bogged down, as at a certain point, I 
realized HOW MUCH more work lay ahead of me to get a working 
system.  I had to add 2 more features to the micro-engine - 
a 256-way branch from the op-code, and some OR gates to OR 
in the register address fields.  Then, I had to build a 
system bus and memory interface.
(I was going to make the I/O architecture much more like a 
PDP-11 than the 360 channel architecture.)  Then, I had to 
design a general-purpose peripheral controller.  I had a 
VERY rough sketch for about a 20-chip micro-machine using 
(probably) 3 byte-wide EPROMS for instructions) that would 
hopefully run at 4 MHz.  Then, I had to build a SCSI 
controller (I already had a SASI disk on my S-100 system), a 
serial mux and a tape controller.
Finally, I had to write at least a primitive OS and figure 
out how to come up with compilers for it.  Had I known that 
UNIX-360 existed, I might have tried to make some kind of 
port of that.  But, obviously, YEARS of work would have been 
needed to make it usable.

See http://pico-systems.com/stories/1982.html     for some 
pics and description of it.

Jon