Archived from groups: alt.comp.periphs.videocards.matrox (
More info?)
Ken <_ken_3_@telia.com> wrote:
> On Wed, 13 Jul 2005 02:38:29 +0000 (UTC), "Synapse Syndrome"
> <paradroid2000@NOSPAMhotmail.com> wrote:
>
>>>> I just upgraded my G550 to a P650 card. Now I am unable to read
>>>> the screen in DOS mode, all is OK as soon as WinXP starts up,
>>>> but i am unable to read the BIOS screens. Any ideas what this
>>>> error is about? I use newest BIOS for the Matrox card.
>>>
>>> Known problem. I have the same with my P750. I have to use
>>> another graphic card when I have to go into BIOS.
>>
>> Does this happen with the Parhelia as well? Is this case for all
>> P650 and P750 owners? Is it just one type of BIOS this happens with?
>
> The problem is that the graphic processor don't support
> low color resolution.
The problem is AFAIK *NOT* that the graphics processor don't support low
color resolution -- it does. The problem seems to be that Asus (in
their implementation of a system that lets the user change the boot
picture) erroneously assume that all gpus use contiguous memory that
wraps over from one line to the next. However, a 480 pixel wide screen
with 16 colours requires 120 bytes, which is an 8-byte boundary. The
Parhelia/P750 requires a 16-byte boundary, meaning that pixel 481 on a
line isn't the same as pixel 1 on the next line -- there's 8 bytes of
padding between each line. The P cards announce this in the BIOS
capabilities call for the resolution, but Asus seems to ignore this.
It's not a problem with most other cards because they have a narrower
memory window and alignment requirements, and not a problem with other
BIOSes, who don't make that assumption.
Matrox has provided two workaround fixes for this problem -- one which
disables the 480xNNNx16 mode forcing the BIOS to choose a different one,
and one that emulates a narrower memory window at the expense of speed.
Asus has done nothing, and tells their customers to contact Matrox,
despite all evidence appearing to point towards Asus being the culprit,
not handling padded lines for 480xNNNx16 resolutions.
Regards,
--
*Art