Re: [hatari-devel] Reeking rubber analysis

[Thomas Huth <th.huth@xxxxxx>]

Am Mon, 09 Sep 2013 21:26:21 +0200
schrieb Laurent Sallafranque <laurent.sallafranque@xxxxxxx>:

> Hi,
> 
> I wanted to do the same patch tonight, but as you've done it, it's
> perfect. I'm happy this game works under hatari now.
> 
> By the way, while having a look at the videl code, I saw that many 
> registers should be set to 0 on certain bits (like for the falcon
> palette).
> 
> For example : in the StColorRegsWrite, a $fff mask should be applied
> to the colors
> 
> The same for the registers that don't use all the bits.
> 
> Do you agree with that ?

Well, it depends on how the register is implemented in hardware. Unused
bits can either be tied to 0, or to 1 or not be implemented at all - in
that case, the result depends on the traffic that has been sent via the
bus before. We've seen that with some registers on the ST already,
especially the ST shift mode register if I remember clearly.

So for emulating unused bits properly, you would need to test them on a
real Falcon to see whether they are 0 or 1 or "random".

 Thomas