On 7/11/19 2:37 AM, Jim Brain wrote: > On 7/10/2019 1:32 PM, 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. >> > As SMF notes, illegal but non "JAM" opcodes will cause the CPU to > desync. Maybe using a NMOS 6502 would work for the approach, but that > requires finding a NMOS '02 They should be easy enough to find. For example I have a number of 1541 with dead R/W heads. Since that's fatal for use as a disk drive they are now only good for parts. One of them even has a 6502C as CPU, that one should be good for 4 MHz. GerritReceived on 2020-05-29 22:27:13
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