Thread: Old Mame stuff
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Old 11 May 2003, 07:02   #9
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Join Date: Jan 2003
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Age: 46
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Actually display driving is a problem even for your good old miggy... if you only have chipram (or slowram from $c00000, same bus does not matter) and your program code runs from again either chipram or slowram each bitplane displayed by the dma steals some bus bandwidth (they use the same bus through bus arbitration, rom code and real fast ram is on different bus).
Due to the way how the 68k fetches data it is not that bad upto 4 bitplanes (16 colours), but anything from 5 bitplanes is a huge performance hit for the cpu speed. On an AGA machine you can compensate for this with using the 32bit bus properly, but on an a500 it is very noticeable.
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