Re: [hatari-devel] _FRB cookie in Falcon emulation

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 01/08/2025 à 22:04, Uwe Seimet a écrit :
> Hi,
>
> > I don't see this with Hatari + tos 4.04 ;when starting with 2MB RAM and
> > no TT/Fast RAM, I get these values once I go to debug mode when reaching
> > the desktop:
> >
> > $5A4 : 0
> > $5A8 : 1357BD13
> >
> > so, no tt ram was added bu default in falcon mode ; I think it's in your
> > settings
>
> Yes, my settings configure Alternate-RAM, and this is reflected in $5a4,
> which is not 0 in this case.
> I was alerted because Hatari started to deal with the _FRB cookie when there
> is Alternate-RAM. I was wondering whether an unpatched TOS 4.04 sets the
> value in $5a4 when Alternate-RAM is configured in Hatari, or if Hatari does
> it instead.
>
> My conclusion is that TOS 4.04 sets the value, but not Hatari. Please
> correct me if this conclusion is wrong.

Hi

no, hatari will do this itself in the case of falcon + tt-ram and not 
using emutos. see src/cpu/stMemory.c around line 264

if ( (...)
        || ( Config_IsMachineFalcon() && TTmemory && !bIsEmuTOS) )
{

   if ( TTmemory )
           STMemory_WriteLong ( 0x5a4 , 0x01000000 + TTmem_size ); 
   /* ramtop */
   else
           STMemory_WriteLong ( 0x5a4 , 0 );               /* ramtop */
   STMemory_WriteLong ( 0x5a8 , 0x1357bd13 );              /* ramvalid */

}

-> so, falcon + tt-ram + tos 4.04 will be handled automatically by 
hatari to declare this extra tt ram (because tos 4.04 doesn't know how 
to detect tt-ram, even if it knows how to use it afterward)

Nicolas