Re: [hatari-devel] Prefetch issue on 68000?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 18/02/2013 23:38, Eero Tamminen a écrit :
> Hi,
>
> On tiistai 19 helmikuu 2013, Nicolas Pomarède wrote:
> > that's a known story, nothing mysterious about prefetch (it was used in
> > many protection code more than 20 years ago) and the fact that memory
> > accesses are made at different "sub-time" depending on the instruction
> > and its micro code is also known.
>
> The reason why asked was the claim about Hatari timings being wrong...

Well, they could be called wrong in the sense that they don't fully 
implement the 68000's microcode for all instructions, but they're right 
when it comes to running most demos/games (else, a lot of demos would 
not work)

> Currently I wouldn't count so much on WinUAE core as its "cycle exact"
> cycles returned by Cycles_GetCounter(CYCLES_COUNTER_CPU) are more bogus
> (often there's zero diff from previous instruction) than the old UAE core
> provided ones.  :-/

WinUAE's 68000 cycle exact mode is correct ; the fact that 
Cycles_GetCounter (which is Hatari specific, not WinUAE) doesn't return 
correct values sometimes is a problem in the Falcon's mode 
implementation, not in WinUAE.

Nicolas