Re: 1.6 PAL Xbox

On Monday 16 January 2006 16:43, you wrote:

> Yes, I see the picture too big - so overscan is enabled when it
> shouldn't be. I realise this is the stated support level on the Wiki,
> so I wanted to help either test or develop something better.

Your enthusiasm is refreshing ;)  Unfortunately, unless you have more 
knowledge about how the chip works (or even better a spec sheet which you can 
legally release!) I doubt you'll get too much further.   

The current settings we are programming the xcalibur chip with are the same 
(exactly, in fact) that the MS Bios uses itself.  It avoids the overscan 
issue you mention by the trick described below.  As a result, we have no idea 
if the chip supports video scaling, and if it does, what register twiddling 
needs to be done to get this to work.  It took me a little while to master 
the problem with the Focus chipset, and that had a helpful PDF!

> What puzzled me is the mod chip originally came with a BIOS which didn't
> have the overscan problem, which seemed to be based on Cromwell.

Yeah, it did, but it cheated.  If you simply do what MS (and this other bios) 
does, and draw things closer to the centre of the picture, nobody notices 
that the edges are missing.

That's the normal state of broadcast television pictures.

> Also I want to use RGB, which also is not supported - though everything
> looks kinda cool in green :-)

Now, that is possible to do, I should think, with a bit of messing about.  
Basically, what's needed is a register dump of the xcalibur chip when it's 
running in one of these modes.  It's been a while since I was last poking 
about with this, so I'm a little rusty.  I recall making a small utility 
which read back the settings from the chip after having got into linux via a 
softmod (the kernel in this being hacked so as not to initialise video, in 
order for it not to trample the settings).

David

>
> Thanks,
> Tim

-- 
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Your manuscript is both good and original, but 
the part that is good is not original and the part
that is original is not good. -- Samuel Johnson
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If it smells it's chemistry, if it crawls it's biology, 
if it doesn't work it's physics

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