bit slice chips (was Re: Harris H800 Computer)

Jon Elson elson at
Fri Apr 22 23:10:55 CDT 2016

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     for some 
pics and description of it.


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