Re: Idea about 1.6 video chip

David Pye wrote:

>On Sunday 28 August 2005 02:25, Jussi Salin wrote:
>  
>
>>Hello
>>
>>Me, an unfortunate xbox owner, went and bought the 1.6 version as my
>>first xbox a week ago. :) Now I have actually read more the pages and
>>found out the reason why I got no RGB output with Cromwell 2.40 (the
>>latest it says) and Xebian. I was able to tune the composite picture on
>>a CBM 1084 video monitor so that all of the X screen is visible (that
>>way workarounding the overscan issue.) However that won't help with the
>>television set in the living room, and I really want RGB for that extra
>>picture quality and possibly for connecting a VGA monitor (I have a
>>LM1881 circuit ready.)
>>
>>Then I got this idea:
>>
>>Would it be possible to solder a new video chip in place to the xbox? It
>>seems to be a SMD chip with rather few pins. Maybe cutting the VDD or CS
>>pins of it would disable it enough to solder a new chip top of it. If it
>>wouldn't work, you could always unsolder the new chip and fix the few
>>old pins. So, do you have any idea of the pin out of this new IC and
>>what might be similair replacement for it? There was some talk about a
>>SIS chip which is similair to those in the older xbox models. Maybe it
>>could be possible to order free samples from SIS, or maybe actually pay
>>for a bunch of them. Do you know exact model number or IC code of that
>>chip? I could look up a datasheet and compare them.
>>    
>>
>
>That just isn't going to work, frankly.  It's an SMD chip, with lots of pins.  
>If you're seeing only a few, you're looking at the wrong chip.
>
>  
>
>>I also got another idea. It says that as it is, there is component
>>output active besides the composite video. The intensity component
>>actually goes to the green pin of RGB, that why there is that greenish
>>picture. Could it be possible to build some analog circuit to convert
>>the component signals into RGB? That way you could get RGB quality even
>>though there would still be that overscan problem and no resolutions
>>greater than 640x480.
>>    
>>
>
>Getting RGB working would be easy for someone who knows what they are doing 
>and has some time.  If you want to help, I'll give you the info you need.   
>The main reason I never got it working was the simple lack of an RGB cable.
>
>I still don't think you'll find that you will get rid of the overscan though. 
>It's the same video quality, etc, as composite. (as you can see if you ignore 
>the green-ness).
>
>David
>  
>
Would it be possible to get rid of the overscan on a v1.6 by reducing 
the resolution? Common sense suggests that if you can display 640x480 
with overscan then you can choose to draw to the middle 600x400 of the 
screen to work around this. It's my understanding that people using HDTV 
modes do something like this (reduce the screen resolution and increase 
the screen margins by the same amount using fbset). As long as you don't 
try to change the video timing might this work with a v1.6 (I don't have 
one to try it on - it's just an idea).

Richard


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