Re: [hatari-devel] DSP performance

[Miro Kropáček <miro.kropacek@xxxxxxxxx>]

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.

  

Is NOP=4 cycles measured 100% accurately (using external test hardware) or using some loop where it is too easy to get bad results, for example if there is multiple NOPs back to back and only every other NOP needs to do memory fetch.

Unfortunately it is not :-(

  

(I still haven't done any real 68020/030 logic analyzer tests, when I finally bother to do it and have all required hardware, I can measure 16-bit accesses 100% accurately)

I'd love to see those results then!

--

MiKRO / Mystic Bytes
http://mikro.atari.org