On 2019-07-10 17:39, smf wrote: > On 10/07/2019 19:32, laughton_at_cyg.net wrote: >> Sorry to tease everyone -- it was the '816 I was thinking of. My >> notion was to run it in parallel with the 6510, not to replace it. In >> other words, the '816 address bus etc would connect to nothing, but >> during reads (code fetches) its data bus would have the 6510 data bus >> copied to it. Then the oh-so-convenient VPA/VDA signals will reveal >> when the opcode fetches occur. > > The 65816 can't even run all c64 code, let alone cycle exact. My bad, I failed to explain the '816 would wake up in Emulation Mode... and would stay there, permanently. That should yield cycle-exact NMOS behavior, which is one of the reasons Emulation Mode exists. However, the use of undefined NMOS opcodes by some programs does present a challenge. If no solution can be found, it might be better to take Gerrit's suggestion and use an NMOS 6502 (rather than an an '816) running in parallel with the 6510. Or, see what can be done with the state machine Jim created. In both cases this is constructive input, which I welcome. :) > If you're > going to use a 65816 then you'd be better off just using the 65816 and > stop the 6510 from executing completely. > > You could then be on your way to designing a SuperCPU clone, which > people would probably love.Received on 2020-05-29 22:29:33
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