Ideas for a simple, but somewhat extendable computer bus

william degnan billdegnan at
Fri Nov 17 19:52:54 CST 2017

On Nov 17, 2017 8:34 PM, "Jim Brain via cctalk" <cctalk at>
> On 11/17/2017 7:25 PM, Paul Koning wrote:
>> One key question is whether it should be asynchronous, as the Unibus is,
or synchronous.
> I thought synchronous would make for a smaller/simpler design, but could
be wrong.
>> A synchronous version of the Unibus would be quite easy; all the funny
one-shot delays would disappear and actions would simply be taken on the
clock edge (rising or falling, pick one).  Just make the clock period
comfortably longer than the worst case propagation delay and you're in
> Given the CPU landscape, I am thinking < 10MHz, which would seem to
satisfy the criteria.
>> I'm assuming it doesn't need to be all that fast.  If you clock period >
prop delay is an issue, things get vastly more complicated.  If so, you
might want to stick with something that's already been sorted out, like
> It does not have to be fast.  I rather thought, "what is the simplest
multi-cpu shared bus that could be easily understood by folks and allow
them to focus on multi-processing education, not bus understanding"
> Jim

Not simpler but there were S100 systems with those cpus, except maybe the
TI 16.

Bill Degnan
twitter: billdeg

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