Re: [hatari-devel] Small bug in Hatari Falcon emulation

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On 11/23/20 2:46 AM, Roger Burrows wrote:
> On 23 Nov 2020 at 1:08, Eero Tamminen wrote:
> > On 11/23/20 12:47 AM, Roger Burrows wrote:
> > > When the "STe Bus Emulation" bit (0x20) in the Falcon Bus Control Register
> > at
> > > $ff8007 is zero, "STe Bus Emulation" mode is set.  This affects bus error
> > > handling.  Hatari already models this as far as the I/O memory area is
> > > concerned (I haven't attempted to check how accurately yet).  But it also
> > > affects bus errors when accessing RAM, which Hatari does NOT model.
> > Basically,
> > > on a real Falcon with "STe Bus Emulation" enabled, there are NO bus errors
> > > generated for the whole $0 to $dfffff region, even in user state.  Even if
> > RAM
> > > isn't present at an address, no bus error occurs.
> >
> > Do reads to non-existing RAM areas produce some specific value like
> > zero, or random values, or
>
> A quasi-random sampling of values shows 0xff is returned.  That looks like a
> floating bus (but what would I know, I'm a software guy).
>
> > is the target location value just unmodified?
> I'm just doing reads, so I'm not sure what you mean.

I meant the read result (e.g. register where you
read it).

You seemed to be doing byte reads.  For IO HW
regs, it matters whether read is byte or word
sized.  Did you try word access?


	- Eero