|Re: [hatari-devel] DSP performance|
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Le 01/07/2015 10:34, Miro Kropáček a écrit :
I still must be missing something..
If this is true, then there is no way for NOP to take 4 cycles to
execute. Either it takes 2 cycles (cache or next opcode word already
in prefetch buffer) or it takes at least 8 cycles.
What's wrong here? It does take two cycles on falcon (if cached) or 4
(if not, execution time is absorbed in the word prefetch time). To be
honest, I'm not 100% confident about the latter but it made sense back then.
I think it would be surprising that a 68030 at 16 MHz takes 8 cycles for
a NOP when the old STF's 68000 at 8 MHZ take 4 cycles.
Or it means the memory access time is really the bottleneck (because 8
cyles @ 16 MHz is the same time as 4 cycles @ 8 MHz)