Re: [hatari-devel] add support for TT ram -> problem with HD emulation and DTA

[Uwe Seimet <Uwe.Seimet@xxxxxxxxx>]

Hi,

By the way, remember that one cannot transfer data from/to TT RAM using
ACSI/DMA. So for full compatibility it should be ensured that such a
transfer does not work.

Take care

Uwe

> Le 17/12/2014 00:53, Nicolas Pomarède a écrit :
> 
> Some updates, I found an issue between TT ram and HD gemdos emulation.
> 
> 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 :(
> 
> In GemDOS_SFirst() :
> 
>         nDTA = STMemory_ReadLong(STMemory_ReadLong(act_pd)+32);
> 
> act_pd = $771e, and the content of $771e is $0100000e.
> 
> But STMemory_ReadLong only handles RAM, so this reads at $0000000e instead
> of 0100000e, and everything goes wrong after that :(
> 
> I will update the STMemory_Read/_Write functions to work with any kind of
> memory, and hopefully this sould fix this issue.
> 
> There's also another problem when saving/restoring snapshot :
> 
>                 Addr = ((Uint8 *)pDTA - STRam);
>                 MemorySnapShot_Store(&Addr,sizeof(Addr));
> 
> This also assumes pDTA is in RAM, which is not the case when TT RAM is
> enabled.
> To fix this, instead of using pDTA which points to the host's memory where
> DTA is, I will store the DTA value (in Atari's memory) and dereference it
> only when needed with STMemory_STAddrToPointer()
> 
> 
> So, only solution for now to have extra TT RAM and HD is to use a direct HD
> image, not the HD gemdos emulation.
> 
> Nicolas
> 
> 
> 
>