Re: [hatari-devel] VBL warnings from Hatari on MegaSTE 8->16Mhz change

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 26/05/2025 à 13:29, Eero Tamminen a écrit :
> Hi,
>
> I mailed the CPX.
>
> Another issue is that STDOOM crashes when cache bit is enabled, but I'm 
> not sure whether that's STDOOM or Hatari issue, because Hatari comment 
> states that the cache bit is not emulated:
> https://github.com/hatari/hatari/blob/main/src/ioMemTabSTE.c#L31

Hi

this comment is not up to date, bit 0 is correctly handled when writing 
bytes/words. I will fix it ; you can set 16 MHz with or without cache, 
and you will see that it makes a big difference when running benchmarks, 
16 MHz without cache is barely faster than 8 MHz (due to RAM being too slow)

in m6800.c you can try to define MEGA_STE_CACHE_DEBUG_CHECK_ENTRIES on 
line 1091, this will run with cache enable and double check that each 
cached value is consistent with RAM.

From the discussion in atari-forum.com, it seems STDOOM was not tested 
on a real megaSTE. Maybe it should be tried first, to ensure the bug is 
not in the cache emulation but in the game itself.

Nicolas


> On 23.5.2025 14.30, Nicolas Pomarède wrote:
> > Le 22/05/2025 à 23:08, Eero Tamminen a écrit :
> > > Hi Nicolas,
> > >
> > > It tried running latest Hatari git with (EmuTOS v1.3 +) MegaSTE 
> > > emulation.
> > >
> > > I think (Emu)TOS sets CPU to 8Mhz initially, but when "general.cpx" 
> > > configuration changes MegaSTE to 16Mhz, or 16Mhz+cache during, I see 
> > > lots of warnings like this:
> > > cyc since vbl old 177270 != new 177338
> > > cyc since vbl old 177364 != new 177432
> > >
> > > They stop only when EmuTOS desktop is reached.
> > >
> > > Few more of those warnings come if I change at runtime from 8Mhz to 
> > > 16Mhz in the CPX.
> >
> > Hi
> >
> > these warnings are from the change to remove CYCLES_COUNTER_VIDEO, to 
> > ensure the new counter method work as before.
> >
> > They are harmless when you have only 1 ou 2 of them after changing 
> > some settings, but I will have a look to try to fix these (it could be 
> > more problematic for demos using precise cycle synchronisation)
> >
> > Could you send "general.cpx" or give a link to it, in order to have 
> > the same context as you ?
> >
> > Note for emutos : would be great to have directly an option to change 
> > MegaSTE 8/16 Mhz or cache from the emutos desktop :)
> >
> > Nicolas