I adjusted the timing in VICE for CRTC-less PETS, and now it is close enough that the HI-RES program actually shows something interesting. If it shows exactly what the author intended, I don't know. I do know that it flickers, which I also remember seeing on real hardware. There is at least a part of the CURSOR logo there. The current implementation in VICE triggers the retrace interrupt immediately after the last visible scanline has been drawn, if I interpret things correctly. It is possible that hardware had a bit of extra delay first. What I've seen in the VICE monitor may suggest that the program runs a bit ahead of schedule, but that depends on how one should interpret concepts as "current scanline" in a line-based (not cycle based) emulation. Is there some documentation where one can find exact timing of the IRQ trigger? I did get the number of cycles per line to 64 (the HI-RES program assumes this) and the refresh frequency at almost exactly 60.000 Hz. In fact, it should be a tad higher, since in the New ROMs there is a timing fix that delays counting of TI by 1/623: 0099-009A Jiffy clock correction: 623rd 1/60 sec does not increment time -Olaf. -- Olaf 'Rhialto' Seibert -- rhialto at falu dot nl ___ Anyone who is capable of getting themselves made President should on \X/ no account be allowed to do the job. --Douglas Adams, "THGTTG"
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