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

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 18/02/2013 23:19, Eero Tamminen a écrit :
> Hi,
>
> Any comments on this:
> 	http://www.atari-forum.com/viewtopic.php?f=94&t=24641
> ?
>
>
> 	- Eero

hi,

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.

I tried to fix the most common cases for this along the years using 
uae-cpu core (the old one) and winuae has direct support for nearly all 
read/write accesses inside any instruction in 68000 cycle exact mode.

For now, Hatari doesn't use the cleanest solution, which would be using 
a cycle exact mode as the winuae's 68000 mode, but most hardcoded cases 
are enough to handle all overscan effects so far (which are the most 
sensitive cases to these behaviours) and other real life cases.

Nicolas