Re: [hatari-devel] profiler cycles (was New WinUAE core issue with Bad Mood)

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On perjantai 15 toukokuu 2015, Nicolas Pomarède wrote:
> Back on this "0 cycle" case.
> 
> As already discussed, the 68030 has some more advanced bus handling and
> cache than the 68020 and can delay write for example.
> 
> What this means is that some instruction can overlap when they are
> executed in a specific order (and maybe from the cache) : for example a
> 2nd instruction will start processing during the tail part of a 1st
> instruction.
....
> If B was 4 cycles alone and overlapped with tail of A, then it would
> completely run in parallel, meaning the number of cycles is in fact 0
> when you look at the total time of the 3 instructions sequence.
> 
> So, unless you have some specific case were sequence of instructions
> really doesn't match the cycle as well as the tail/head computation as
> describe in MC68030 manual, I would say this is perfectly normal,
> there's nothing we can do.
> 
> 0 cycle instruction are in fact fully paralleled instructions.

As the results were radically different from previous WinUAE core,
I was worried that there was some problem with global cycles counter
updates.  Good that this isn't the case! :-)

-> I've changed the successive zero cycles test to be applied
only to old AUE core (when DEBUG is enabled).


	- Eero