MasterOfGizmo wrote:It's not a cup bug. The tas instruction forcefully does two uninterruptible subsequent bus cycles to make sure it's an atomic operation. Some versions of the vdp did not cope with that. E.g. the Amiga also didn't cope with it and you shouldn't use the tas instruction there.
Yes, I phrased it wrongly. Probably the VDP breaks it on the real thing, just I curious is it possible to trigger this problem without modifying the CPU?