Re: [hatari-devel] (Missing) TT SCSI emulation problems

[Uwe Seimet <Uwe.Seimet@xxxxxxxxx>]

Hi Thomas,

Indeed, TOS 3.0x will probably fail because there is no reason for TOS
to expect that the SCSI hardware is not available.
It may be possible to resolve this by only raising a bus error for one
of the SCSI chip registers, so that TOS does not crash but at least
HDDRIVER (any maybe CBHD) is able to detect that there is no SCSI chip.
How should I modify the Hatari sources to test this, i.e. how can I
raise a bus error when reading from a particular memory address?

Take care

Uwe

> Am Sun, 23 Aug 2015 20:18:10 +0200
> schrieb Uwe Seimet <Uwe.Seimet@xxxxxxxxx>:
> 
> > In the TT emulation, when launching HDDRIVER or CBHD in their default
> > configurations both drivers take a very long time to initialize. CBHD
> > even seems to be hanging forever. This is because they try to access
> > the TT's SCSI chip and even though this chip is not (at all?)
> > supported by Hatari, there does not seem to be a bus error when
> > accessing its registers. As a result the drivers assume TT SCSI is
> > supported, they try to test for devices and are blocked in some
> > timeout loops. I guess there is a reason why the TT emulation does
> > not just throw a bus error as long as the SCSI chip is not emulated.
> 
> I don't remember clearly, but I think there were some other issues when
> using bus errors for this memory region on TT. Did you try it?
> I think at least TOS 3.0x will likely fail since it does not expect an
> bus error here and thus likely needs to be patched.
> 
> > Why is this so, and what about a startup (command line is sufficient)
> > option that disables the SCSI chip emulation in TT mode?
> 
> That could be an option ... or is there maybe a simple way to emulate
> just enough of the SCSI chip to fake a "there is no device at this bus"
> signal for the HD drivers?
> 
>  Thomas
> 
>