Ideas for a simple, but somewhat extendable computer bus

Jim Brain brain at
Fri Nov 17 19:34:21 CST 2017

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 business.
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 PCIe.
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"


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