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Old 11-26-06, 08:25 PM   #22
NVIDIA Corporation
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Join Date: Oct 2002
Posts: 53
Default Re: Nvidia GeForce Go 7600

Hi Mestam,

Short answer: I'd recommend changing your xorg.conf to request the modes:

Modes "nvidia-auto-select" "1024x768" "800x600" "640x480"

(you could replace "nvidia-auto-select" with "1440x900"; they will both
correspond to the same thing in your configuration; 1440x900 is the
native resolution of your DFP, and will be the mode that looks the best
on your DFP)

You can't do 1280x1024, and even if you could, it wouldn't look good
because the GPU would have to scale horizontally from 1024 pixels in
your desktop to 900 pixels displayed on your DFP.

Long answer: there are several reasons why no 1280x1024 modes are
getting validated for your DFP. Some of them are configuration issues,
but there is also a hardware limitation, too.

1) In the verbose log you attached, all the 1280x1024 modes are getting
discarded because the pixelclock (the number of pixels, in millions, that
the mode requires to be sent to the DFP every second) of the 1280x1024
modes is considered to be larger than what the DFP can accept; the DFP's
max pixel clock is, in this case, inferred from the list of modes in
the EDID. You could work around this with "NoEdidMaxPClkCheck" flag to
the "ModeValidation" option.

2) The NVIDIA X driver defaults to using the HorizSync and VertRefresh
ranges from the DFP's EDID. After addressing issue #1, you might
encounter problems here. You can set the "UseEdidFreqs" option to FALSE
to make the X driver using the frequency information from the Monitor
section instead.

3) Even if you address the frequency validation issues above, the X driver
is still going to prohibit 1280x1024, because it has inferred from the
EDID that the DFP's native resolution is 1440x900. This means that the
NVIDIA GPU must scale from the mode size to the DFP's native resolution.
The NVIDIA GPU can scale from a smaller mode size UP to 1440x900, but
the NVIDIA GPU cannot scale from a larger mode size DOWN to 1440x900
(1280x1024 has more pixels, horizontally, than 1440x900). Even if the
GPU was capable of downscaling from a 1280x1024 desktop to a 1440x900
native resolution on the DFP, it wouldn't look crisp, and there would
be filtering and you would likely lose some information in your desktop.

For the crispest image, it's recommended to run your desktop at the
native resolution of your DFP. In this case, that's 1440x900.

I hope that helps.
Andy Ritger
NVIDIA Linux Graphics Driver Engineer
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