blank external DVI on Thinkpad T40

Alex Deucher alexdeucher at
Wed Feb 25 12:32:58 PST 2009

On Wed, Feb 25, 2009 at 3:11 PM, Gilad Arnold <arnold at> wrote:
> Alex, thanks for the quick reply.
> On Wed, Feb 25, 2009 at 02:55:49PM -0500, Alex Deucher wrote:
>> Sounds like display underflow.
> I wonder what that is and what causes it?

Not enough memory bandwidth for everything you want to use.  The
memory controller is not able to keep up with the display controller
due to contention from other parts of the chip (other display
controller, 2d, 3d, etc.).

Also, IIRC, the DVI port on the IBM docking station is only supposed
to support a max resolution of 1280x1204 or 1600x1200.  It might be a
limitation of DVI traces or connector in the docking station.

>> Try disabling the LVDS if you aren't using it.
> I tried adding this to xorg.conf:
> Section "Monitor"
>  Identifier   "LVDS"
>  Option       "DPMS"
>  Option       "Ignore" "true"
> EndSection
> Xorg fails to initialize with the "no screens" error (monitors were
> found but none has a usable configuration). I also tried 'xrandr
> --output LVDS --off', but the DVI-0 output remains blank. Any other way
> I can disable LVDS?

Either of those should work.  You'll have to have another monitor
plugged in if you ignore the LVDS or it won't find any attached


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