[hatari-devel] Videl changes

[Anders Eriksson]

On Sat, 5 Feb 2011, Laurent Sallafranque wrote:

> I'm nearly sure that none of the ST overscan demos would run natively on the 
> Falcon.

Correct.


> Falcon plasmas are all running well (from what I know), which mean they don't 
> use video tricks but colors "rotations" or something else.
>
> Last point : I haven't found a program that changes the palette except in the 
> left border. If you know one...

The videl have a bug regarding updates of the colour registers. When 
updating a colour register, the videl will show garbage pixels meanwhile 
the colour is set. This makes it impossible to implement classic ST 
plasmas or Spectrum 512 things. As if the variable bus load and caches 
weren't enough to put you off already :-)

Other games which work on Falcon that uses some STe video features are 
Stardust (top/bottom borders), Obsession (top/bottom/left borders as well 
as screen splits), Utopos (top/bottom borders and screen splits), 
Substation (top/bottom borders in the intro).

I think in Obsession on Falcon/VGA you can see the videl bug with garbage 
pixels during colour change. On VGA the HBL moves twice as fast and there 
are no borders, so the colour switch comes in the middle of the screen 
there hence showing the bug.

--
Anders Eriksson
ae at dhs.nu     http://www.dhs.nu/
ae at atari.org  http://www.atari.org/