Re: [hatari-devel] VME access

[Thomas Huth <th.huth@xxxxxxxxx>]

Am Sun, 3 Jan 2021 11:47:27 +0100
schrieb Christian Zietz <czietz@xxxxxxx>:

> Thorsten Otto schrieb:
> 
> > On Sonntag, 3. Januar 2021 10:02:19 CET Thomas Huth wrote:
> >  
> >  > Couldn't you please try to come
> >  > up with enough VME emulation instead to fix Linux on the TT?
> >  > That would be the better direction.  
> >
> > Wouldn't it make more sense to pretend no VME is available? To
> > emulate VME, you would need to specify which kind of VME card
> > should be emulated (AFAIK could be either memory expansion, or
> > graphics-card, or network card). That would be a pain.  
> 
> Hm, think there's a misunderstanding here -- or rather: unclear
> terminology. Eero's patch does not deal with emulating the VME bus per
> se, but with configuring bus errors for *SCU* registers. The SCU
> (System Control Unit?) is an ASIC in the TT and MegaSTE that -- among
> other things -- takes care of interrupt routing, for the onboard
> interrupt sources as well as for interrupts from the VME bus.
> 
> For sure, a proper emulation of the SCU (at least as far as interrupt
> routing is concerned) should be the long-term goal for Atari, imho.

Right. And we've had bus error hacks / wrong bus error behavior in the
past already (remember the SCC registers on the TT?), and that was only
causing confusion and problems for various users. So I'd rather like to
see at least basic emulation of these registers instead of adding more
hacks.

 Thomas