[hatari-devel] Re: Cycle exact 68040/68060 mode in Hatari

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 13/09/2016 à 22:57, Thomas Huth a écrit :

> 	if (using_ce020 >= 3)
> 		return false;
>
> Why is this code there? I have a hard time to understand the reason for
> these two lines... don't we want to have a do_cycles_ce020_internal()
> in cycle-excact 68040/060 mode?
>
> Thanks for any help,
>  Thomas

Hi

Toni certainly knows the details better than me and can elaborate, but 
IIRC some emails discussions we had, 68040/60 is a completely different 
beast regarding CE mode.
While 68030 is very close to 68020, 68040/60 have more pipelines and can 
run some instructions in parallel, none of this being really documented 
(CE mode for 68020/30 was certainly not publicly documented either, but 
it took Toni so much time to make it work that I guess 40/60 would 
require a lot of time/ressource)

As the results would be far from cycle exact, maybe that's why CE mode 
is just disabled for 68040/60 and they often just take 1 cycle per 
instruction to "simulate" a much faster cpu.


Nicolas