Does TC work with C64C PAL machine?

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  • I checked the known bugs and found this test machine:

    C64C (ASSY NO 250469 R4) (Tobias)

    • CPU MOS / 8500 / 1588 24
    • CIA1 „new“ MOS / 6526A / 1788 216A
    • CIA2 „new“ MOS / 6526 / 1888 216A
    • VIC-II „new“ MOS / 8565R2 / 1688 22
    • SID „new“ MOS / 8580R5 / 1788 25
    • clock generator: MOS 8701
    • RAM: M41464-10 / OKI / JAPAN 833050

    Box Check:Type detects this machine as „C64C IC 8565 8580 6526A 6526A“ (which seems correct)

    VICII/lp-trigger/test2.prg shows 2-pixel delay

    CIA/irqdelay/irqdelay.prg reports CIA1NEW CIA2NEW

    VSP Lab v1.1 reports errors, so this C64 is NOT VSP safe!

    What does the last line mean, Tobias?

    Thanks and regards

  • What does the last line mean, Tobias?

    I'm not Tobias, but I think I can explain it the same way :-)

    VSP is an effect that works on some, but not all C64 models. Where it does not work, the computer usually crashes dramatically, because large parts of the memory contents get destroyed.

    For a very long time, people believed that the VSP-error was caused by the VIC-II chip "forgetting" refresh if the picture is moved using VSP, but a few years ago, I was approached by TOmmi Lempinen from Sweden a few times, and he kept bugging me with questions for at least two Revision parties in a row. At some point, his explaining of findings lead me to the assumption that it's a timing parameter of the RAM chips that's violated, and Tommi investigated exactly that assumption by doing logic analyzer shots of the involved signals. Sure enough, when I met him next year at Revision, I confirmed that the timing parameters "address hold time after falling edge of RAS" and "address setup time before falling edge of RAS" are violated.

    So while it may sound "really bad" that a C64 is not VSP-safe, it only means that an effect that is rarely used is not working on that specific machine. THe only game that I personally know is "Mayhem in Monsterland".

    The good news is that the Chameleon does make the C64 VSP-compatible, because the internal memory is not used while the Chameleon is connected.