Re: [hatari-devel] Blitting from TT RAM seems to work on Falcon?

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 10/10/2023 à 21:37, Thomas Huth a écrit :
> On 10/10/2023 18.08, Nicolas Pomarède wrote:
> > Le 10/10/2023 à 08:28, Anders Eriksson a écrit :
> >
> > > Hi,
> > >
> > > no you can't use blitter from Afterburner or CT2 TT-RAM (as well as 
> > > CT60/3).
> > >
> > > However there are some memory cards/accelerators where the "TT-RAM" 
> > > lies within the lower 24-bit memory space. It's been quite some time 
> > > but I think one is called Magnum and the other Falcon FX. I'm not 
> > > sure if the blitter works though.
> >
> > Hi
> >
> > thanks for the confirmation, this wrong case has been removed from 
> > devel version.
>
> Have you tested it? I now get distorted graphics now if I run TOS 4.04 
> in Falcon mode with TT-RAM enabled. IIRC TOS 4.04 blindly assumes that 
> all memory is usable by the blitter and does not avoid the TT-RAM for 
> buffers that are used by the blitter. That was likely the reason for the 
> code that we had there.

OK, this makes sense. I vaguely remember something like this. I will put 
the code back, maybe with a better comment for further reference.

As for TOS not checking that blitter doesn't use "TT RAM", I think 
that's because it's not possible on a "normal" falcon to have TT RAM (in 
the sense of having RAM using 32 bit addresses), since the 68030 in the 
falcon is in fact limited to 24 bit addresses (only signal A0-A23 are 
connected).
So it's likely they didn't check ram above 0x01000000 in tos 4 because 
it was simply not possible hardware-wise.


> I assume that CT2 or Afterburner patch the TOS so that it does not use 
> the TT-RAM for the VDI?

At one point I came across the source for modified TOS , but I don't 
remember what it patched exactly. Maybe someone can have a look.

Nicolas