> I don't know the cause of pcb vs. mame differences but most of what has been > mentioned like the dirty fading happens on the real hardware. Wait states only > affects game speed as far as I know.
Maybe, maybe not. I think there are some issues related to sprite limitations and not synchronising the cpu and the video chip properly (what we'd refer to in the 90's as "raster effects"). The later would be affected by incorrect cpu speed.
While as a project we advocate accuracy, in a lot of cases we fall short.