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Old 07-10-07, 07:57 AM   #1
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Join Date: Jul 2007
Posts: 3
Default Dual/Single Link TMDS


I've got a strange error concerning DVI link detection with my Quadro cards.
Here is my configuration :

- Some machines (A) with Quadro 3400
- Some machines (B) with Quadro 4500
- a Dell 2001FP for tests
- and a DVI switch MatrixPro from Barco. ( )
- tests were done with drivers 8762 and 9631 (same behaviour)

I want to plug the Dell to the DVI switch, and use the machines (A&B) as data input for it, using the MatrixPro for switching.

Currently, everything works fine if i plug the Dell directly to the graphic cards with a Single Link DVI-D.

The problem is the X server is unable to read the EDID info from the matrix (even if this hardware supports this).
I've got the very strange following behaviour :
- I plug the Dell directly, I start the X server, everything is ok. I unplugged the Dell from the PC, plug it to the DVI switch, and plug the DVI switch to the PC. Everythink is still ok.
- If I restart the X server with the DVI switch used, i've got no image on the screen.

To workaround this, I decided to disable the EDID detection in X config file, and set all the informations using NVidia driver options. Doing this, it still works fine with the Dell directly plug, but doesn't when using the dvi switch.

After analysing, the X server log in verbose mode, i notice that the only difference is :

When it works:
(--) NVIDIA(0): DFP-0: Internal Dual Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is supported
When it does not work:
(--) NVIDIA(0): DFP-0: Internal Single Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is not supported
And I made other verification, every time it works, it is detected as a Dual link, and every time it does not, it is detected as a Single Link, even if all the cables are Single Link only (DVI-D) !

Is it possible to force the dual link mode ?
Do you have a clue why the EDID data are not read ?
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