monotech
commented
10 months ago Hello, and thanks for contacting. Sorry to hear you're having trouble with the MOS CPU Replacer in your Plus/4. That's quite a peculiar bug. Yea only 6510 mode seems to be reliable. I haven't heard of your specific issue but I'll try to get someone who owns a Plus/4 to try it and compare with original 8501. If it is indeed reproducible, it could give clues perhaps. There are more expensive FPGA-based implementations of 8501 that seem to be bug-free. Likely a signal timing issue.
Note that the difference between Rev1 and Rev2 only affects 6510 and 6510T.
On Thu, 14 Dec 2023 at 11:29, perhof @.***> wrote:
I've built several revision 2 CPU replacers. I've had JLCPCB assemble everything except the ICs which I've sourced from Digikey/Mouser and soldered myself. The pitch is not a problem. The adapters that I've configured for C64 work very well. I haven't found any compatibility problems there yet.
It's the ones I've built for the Plus/4 that are having an issue. The issue I'm having is with the DIRECTORY command on the Plus/4. The command returns only one charcter or sometimes a line or two from the directory before returning to the READY prompt. It's not 100% consistent except that it never works fully. The DIRECTORY command reads a disk directory to the screen one byte at a time instead of loading the full directory into memory. LOAD"$",8 loads the entiry directory to memory and that works fine and loading programs works fine too. At least all the programs I've tried.
-Tested three different CPU Replacers (all are Rev 2) -Tried in three different Plus/4 computers (all three are new to me and had dead CPUs) -Tested several AliExpress 6502's that have been verified to work fine in all other applications including some C64 demos that don't work with all 6502's and I have tried with 6502's out of 1541 drives as well. -Tested with SD2IEC, Pi1541 and NLQHD drives. -Tested different Kernals: Rev 5 (US), Rev 4 (Swedish) and JiffyDOS.
The @$ JiffyDOS command which also loads the directory to screen works fine but the DIRECTORY command fails in JiffyDOS too.
I don't have access to a genuine 7501 or 8501 so I can't verify that it is indeed the CPU replacer that is causing this issue. I'm hoping someone else can try to reproduce the issue, otherwise I'm out of ideas.
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perhof
SteveGuidi
I've built several revision 2 CPU replacers. I've had JLCPCB assemble everything except the ICs which I've sourced from Digikey/Mouser and soldered myself. The pitch is not a problem. The adapters that I've configured for C64 work very well. I haven't found any compatibility problems there yet.
It's the ones I've built for the Plus/4 that are having an issue. The issue I'm having is with the DIRECTORY command on the Plus/4. The command returns only one charcter or sometimes a line or two from the directory before returning to the READY prompt. It's not 100% consistent except that it never works fully. The DIRECTORY command reads a disk directory to the screen one byte at a time instead of loading the full directory into memory. LOAD"$",8 loads the entiry directory to memory and that works fine and loading programs works fine too. At least all the programs I've tried.
-Tested three different CPU Replacers (all are Rev 2) -Tried in three different Plus/4 computers (all three are new to me and had dead CPUs) -Tested several AliExpress 6502's that have been verified to work fine in all other applications including some C64 demos that don't work with all 6502's and I have tried with 6502's out of 1541 drives as well. -Tested with SD2IEC, Pi1541 and NLQHD drives. -Tested different Kernals: Rev 5 (US), Rev 4 (Swedish) and JiffyDOS.
The @$ JiffyDOS command which also loads the directory to screen works fine but the DIRECTORY command fails in JiffyDOS too.
I don't have access to a genuine 7501 or 8501 so I can't verify that it is indeed the CPU replacer that is causing this issue. I'm hoping someone else can try to reproduce the issue, otherwise I'm out of ideas.