Re: [hatari-devel] TT emulation crashes when there is no ACSI drive

[Uwe Seimet <Uwe.Seimet@xxxxxxxxx>]

Sounds quite tricky. Why doesn't this also happen on real Atari hardware?
I'd assume that there could also be an MFP interrupt at a critical
moment.

> Christian Zietz schrieb:
> 
> > Ah, that was the key missing piece of information! Now I can see the
> > bug, too. And I guess Eero and Nicolas could find the reason behind it.
> 
> My initial analysis for the Hatari developers to continue on:
> 
> It is stack corruption after all -- like I speculated before. While
> running AUTO programs, TOS is operating with a dangerously low stack,
> very close to the GEMDOS register save area. The Hatari cartridge Pexec
> code also needs some stack space. Thus, if a MFP interrupt occurs at
> precisely the wrong moment (i.e. within a GEMDOS call from
> load_n_reloc), the stack overflows into the save area and upon return
> from GEMDOS the A6 register is wrong, ultimately causing the crash Uwe
> is experiencing.
> 
> Even minute changes in timing, like switching to "cycle exact" mode or
> renaming the file (which probably makes some code running a bit longer
> while comparing file names) makes the MFP interrupt happen at a less
> critical moment.
> 
> Yet, this was a time bomb waiting to be triggered. I don't have a
> solution at hand, though. Maybe switch to another stack during the
> cartridge Pexec code?
> 
> Regards
> Christian
> --
> Christian Zietz  -  CHZ-Soft  -  czietz@xxxxxxx
> WWW: http://www.chzsoft.de/
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> 
>