Re: [hatari-devel] add support for TT ram ?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On keskiviikko 17 joulukuu 2014, Nicolas Pomarède wrote:
> I just committed support for extra TT RAM when the selected machine is
> set to "TT".
> This was tested with TOS 3.06 and EmuTOS 0.9.3.
> This works by simulating the bus errors that the TOS will encounter when
> scanning the possible extra RAM starting at address $10000000.
> 
> As such, the following parameters are needed in Hatari :
> 
>   - 24 bit addressing should not be used, else there's no way to see
> more RAM if upper 8 bits of an address can't be used
> 
>   - "patch TOS for faster boot" should not be used, because it would
> bypass the TOS' detection for TT RAM, and no RAM would be added.
> As a side note, it's not advised to set this setting, as it can lower
> the compatibility with some games that expect the whole TOS boot
> sequence to be made (so, I will change it to default to false for new
> users)

I've changed TOS memory setup code to automatically disable 24-bit
addressing and fastboot if TT-RAM is used under TT emulation.  It
will notify user about about this.

As there's no point in using 32-addressing unless there's TT-RAM,
and it makes things less compatible, I'm forcing 24-bit addressing
when TT-RAM is not in use.  Should I remove 24-bit selection from
SDL GUI, options and config file too?


>   - if using EmuTOS, there's a bug in version 0.9.3 (and lower) where
> EmuTOS will crash when 32 bit addressing is used and a cartdridge is
> detected at address $FA0000. This means TT RAM and HD emulation can't be
> used at the same time for the moment.
> You should either use TOS 3.06, or wait for EmuTOS 0.9.4 that fixes this
> issue.

No need to wait, Vincent did EmuTOS CVS snapshot including the fix:
http://sourceforge.net/projects/emutos/files/snapshots/CVS-20141215/


>If you boot TOS 3.06 with HD gemdos emulation, you will get some messages :
> GEMDOS Fsfirst() failed due to invalid DTA address 0x121c00e0
>
> And you can't access c: or whatever letter your HD has been assigned.
>
> After tracing various calls, the problem is in gemdos.c where basically 
> all code that does HD interception expect the DTA to be in standard RAM, 
> not in valid TT RAM :(
>
> So, only solution for now to have extra TT RAM and HD is to use
> a direct HD image, not the HD gemdos emulation.

Just use EmuTOS, only TOS v3 has that problem.


> Such extra RAM won't be available at the moment for Falcon, because TOS
> 4 doesn't scan $1000000 for extra RAM (due to its 24 bit addressing
> limitation). EmuTOS doesn't scan it either, as Falcon are not supposed
> to have such RAM anyway.
> 
> Next steps :
>   - add support for TT RAM in Falcon mode, by patching TOS variables
> 
>   - add support for TT RAM in TT/Falcon mode when using "patch TOS for
> faster boot"

After these are done, the forcing part can be updated.


	- Eero