Re: Re[2]: NOVA cards

From: Jo Even Skarstein <>
Date: Fri, 26 Sep 1997 15:01:54 +0200

On Fri, 26 Sep 1997, Johan Klockars wrote:

> > > What I ment was that you can't use vbl if you have got a Nova card as
> > > you wont get a VBL interrupt, or will you? I don't realy know, but I
> > > don't think the Nova interface can generate a vbl interrupt.
> >
> > In that case it'll break a lot of programs! I'm sure the VBL is still
> > active even with Nova's installed.
> It's of course possible that _a_ VBL interrupt is active, but it won't be the
> "real" VBL interrupt unless there is a way to get that from the NOVA card
> and onto the original interrupt line, which seems doubtful.

That's why we have the VBL-list :-) As long as the Nova-drivers
supports the VBL-list all cleanly written programs should work fine.
I guess that just hooking into the original VBL-vector won't work very

> > > I guess there is no way to patch some games to run in a GEM window,
> > > like Popoulus?
> Why not?
> With a processor that supports an MMU, I don't see any problem with that,
> in principle.

Not in principle...

> With proper memory space setup, it should be quite possible to fool a program
> into believing that it's accessing the normal screen and then have another
> task responsible for converting that for display on the real screen.

This should be fairly easy.

> If necessary, even most hardware accesses could be trapped and emulated via
> GEM etc.

This is the hard part. Most games grabs everything to themselves, runs
in supervisor-mode, have custom-written loaders, f**k around with the
shifter etc. To get it to work properly an entire ST-emulator would
have to be written. Not a bad idea though...

> > Doubtful. The only game I've partly managed to run on the AB is "No
> > Second Price". It worked, but the gameplay was interrupted constantly
> I've not tried that many games, but I was surprised at how many did work fine.
> If there was an equivalent of Backwards for the AB040, I think lots of things
> would work well.

The main problem is that a lot of games use things like self-modifying
code and similar sh*t, and the 040 doesn't seem like to this very much
even with all caches disabled.

I tried an old demo I wrote several years ago, and even if it didn't
use any dirty hardware-tricks (Except some border-busting which I
disabled before trying) it failed to work until I commented out all
self-modifying code. That left me with some music and a starfield ;-)

> Sounds like the MOVEM problem to me (I had similar problems with Frontier).
> Have you tried disabling one or both caches?

Both disabled. It's no real problem though, I still have several ST's
available for playing those games.

** Jo Even Skarstein
** beer - maria mckee - atari falcon - babylon 5
Received on fr. sep. 26 1997 - 15:01:54 CEST

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