[hatari-devel] Re: 040 MMU support?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

Thanks Christian for the analysis!

I'm cross-posting this to hatari-devel.  Feel free
to reply to whichever list feels more suitable as I (and most of the 
others) are on both.

On 4/1/20 10:09 PM, Christian Zietz wrote:
> Christian Zietz schrieb:
> > Eero Tamminen schrieb:
> > > I was wondering whether anybody can think of
> > > a reason why EmuTOS boot would stop in ide_init(),
>
> > I've started to investigate and will continue doing so.
>
> There's something seriously wrong with the emulation of exceptions in
> the failing Hatari configuration, i.e., with 68040 and MMU. EmuTOS does
> not get *any* bus errors while probing for possible IDE interfaces [1]
> and, thus, detects four of them. Therefore, it will spend four times the
> IDE timeout (31 seconds) while waiting for any attached IDE drives to
> become ready.

I guess this could in theory happen also if MMU is
configured to map IO area to wrong place, not just
with broken Hatari 040 MMU emulation?

(Although things working with older Hatari version
make it unlikely.)


> When you wait long enough (= more than two minutes), it gets past
> ide_init() and through the entire bios_init(). But it crashes with a
> nonsensical exception, before getting to the Desktop:
>
> Panic: Exception number -937
> sr=ffff pc=ffffffff
>
> D0-3: 00000000 00000000 00000000 00000000
> D4-7: 00000000 00000000 00000000 00000000
> A0-3: 00000000 00000000 00000000 00000000
> A4-7: 00000000 00000000 03fb4fc6 fffffff0
>   USP: 03fb4ff8
>
> Also note that the failing Natfeats could point in the direction of
> exception emulation issues, too, since afaik Natfeats rely on an illegal
> instruction.
>
> I think this is the point where you could start bisecting Hatari (if
> you're not already doing so), given that older versions of Hatari work
> with the same configuration.

I haven't done that yet, I'll do it later this week.  It's possible that 
e.g. one of the WinUAE
CPU core updates missed some Hatari integration
bits.


	- Eero

> Regards
> Christian
>
> [1] IDE interfaces are probed in the 0xFFF00xxx address range.