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List:       xfree86-devel
Subject:    Re: External CRT works on 1024x768 but LCD not. Please Help!!!
From:       Tim Roberts <timr () probo ! com>
Date:       2005-02-21 18:53:42
Message-ID: 421A2E36.1020400 () probo ! com
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Nqnsome wrote:

>
> Christian Zietz wrote:
>
>> I still suppose that your BIOS only recognizes the LCD as a 800x600 one,
>> while the CRT is recognized correctly as being able to display 1024x768.
>> The Windows XP driver doesn't care about the BIOS but bypasses it. X on
>> the other hand needs the BIOS to set the resolution because the
>> information on how to do that without the BIOS is not publicly 
>> available.
>
> Sorry, but what do you mean with "how to do that"? What kind of 
> information is (not!) in the BIOS that tells X how to change the 
> resolution? A function? A memory address? Something else?


Changing the resolution on a video card requires writing a number of 
timing and configuration registers directly to the chip hardware.  The 
definitions, usage, interactions, and philosophy of those registers are 
often quite complicated, and vary wildly from manufacturer to manufacturer.

The video BIOS knows how to write those registers when you make a VBE 
INT 10 call, because the engineers that designed the chip wrote that 
BIOS.  The Windows driver knows how to write those registers, because a 
team at the chip manufacturer wrote that driver with the assistance of 
the design engineers.

However, chip manufacturers often do not write XFree86 drivers, because 
it represents approximately 0% of their annual sales.  Further, more and 
more chip manufacturers consider their chip specs to be proprietary, so 
they are not released without a license agreement and a set of stiff 
legal handcuffs.  Without the chip specs, the only way a non-Windows 
driver can set the video mode is by asking the BIOS "pretty please".

If the BIOS has been crippled by not supporting certain modes, then X 
will be crippled in the same way.  I was astounded to learn that many 
laptops with Intel graphics chips ship with 1400x1050 LCD panels, and a 
video BIOS that does not support 1400x1050 mode.  That's just criminally 
negligent.

There is nothing we can do, short of reverse engineering, which has its 
own set of legal issues.

> I am asking this because, if I have more information about what is 
> possibly broken/missing in the BIOS, I can try to contact the 
> manufacturer and ask for a fix. Without specific information it is 
> difficult to get a useful answer from the manufacturer (COMPAL).


You will find no help at COMPAL.  All they do is repackage the BIOS and 
drivers from Intel.  It is quite likely they don't even have a graphics 
driver writer on staff.

-- 
- Tim Roberts, timr@probo.com
  Providenza & Boekelheide, Inc.

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