On Thu, Dec 8, 2022 at 6:44 PM David Roberts <daver21145_at_gmail.com> wrote: > > What do you actually mean by a test clip? commodore used to have these IC clips that would go over the $Fxxx ROM (or it was the CPU? I haven't actually seen one, but I have the ROM's dumps). The clip would override the boot ROM with a diagnostic code and run some tests on Video RAM, main RAM (16k only) and test the I/O ports if you have the right dongles on the various ports. The RAM test on these ROMs is so useless that I don't really believe what it reports, in my experience it gave a correct indication on less than half the times I've used it. However it's sometimes helpful to have it running because it continuously loops on the failing test. On my youtube channel (_at_iz8dwf) I have shown the clip's ROMs in action on the CRTC based PET repairs. I don't think these ROMs would work on non-CRTC PETs. HTH FrankReceived on 2022-12-08 21:00:02
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