pjw wrote:Thanks, Peter. Most informative! Might we see a Q68/20 some day?
From a pure development view, the Q68 logic could be changed to 68020 compatibility quite easily. (This would not include cache, which I hope to implement separately someday. But I suspect cache was not your focus.)
It would rather be a logistical problem. Firstly, the Q68 is a compromise for retro computing and the 68020 introduces a few incompatibilities for ancient software. So I can not change the Q68 in general. Secondly, the fact that the Q68 FPGA is factory programmed does not allow the user to switch between 68000-compatible and 68020-compatible hardware.
The Qzero might be a solution for this issue, because it allows user updates of the logic. But it is a much different piece of hardware - a tiny board for electronics tinkerers that does not include all the connectors a desktop computer user expects. Now the Qzero is terribly versatile and could be turned into a desktop computer by adding a baseboard that carries the connectors. I did not yet decide to go that route, since a two board solution is always more expensive and more work to build than a single board. (Just by the way, the lack of clarity what to use the Qzero for, has also lead me not to release it yet. Supporting the large range of possible applications calls for so much boring detail work, documentation and testing that it loses the fun factor for me.)
Can you explain a bit, why you want 68020 compatibility? Is it performance or the elegance for assembler programming?