phaeron Posted May 12, 2015 Share Posted May 12, 2015 Unsure if invoking the scanline 240 hires bug would cause DLIs to keep triggering beyond normal display, my guess would be since only PMG can be shown in that area it's a case of probably not for DLIs. Not that I can tell from the schematics. DLI occurs if the delta counter compares equal, that's suppressed in vertical blank, and vertical blank is scanlines 248-7. The hires bug causes ANTIC to send confusing signals to GTIA, but ANTIC itself isn't confused. Similarly, VBI is triggered simply by Y=248, so not much room to go wrong there, either. Sequencing the VBIs with the DLIs is an option but it has to be done exactly right. One extra or missing DLI and you're toast. This includes the first frame, which can be subtly munged if you're not completely studious about clearing every single display state. Testing for the VBI means that at least if you run over somewhere there's a chance the VBI handler will get everything back on track. If you really want to pinch cycles, the STA NMIRES in the VBI handler can go. VBI resets DLI and DLI resets VBI, so it's not normally needed unless you're testing for it in the IRQ routine too. 1 Quote Link to comment Share on other sites More sharing options...
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