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-   -   1.0-8756 fails to detect internal dual-link TMDS on 7900GT (http://www.nvnews.net/vbulletin/showthread.php?t=69003)

hpcjerry 04-23-06 07:34 PM

1.0-8756 fails to detect internal dual-link TMDS on 7900GT
1 Attachment(s)
I am trying to get an IBM T221 monitor working with a 7900GT card.
This monitor worked fine at 1920x1200@41Hz with an ATI Radeon 8500 in a
different system.

But it does not work very well with the linux nvidia driver 1.0-8756.
I took the xorg.conf used for the Radeon and made the minimal changes required
to convert it over to using the nvidia card. In particular I did not change
the modeline.

Also, there is one problem with the T221 monitor - it does not report an EDID
that the Xorg server can understand. So, I have had to use the following

Option "UseEDID" "false"
Option "ExactModeTimingsDVI" "true"
Option "ConnectedMonitor" "dfp"


I have found that if I start up the Xorg server with another DVI monitor
connected to the 7900GT and then switch it over to the T221, the display is
fine. BUT, if I start the X server with the T221 connected, it fails.

I have run X -logverbose 6 for both the "good" (works when connected to another
DVI monitor first) and the "bad" (connected to the T221 to start). I will
attach the logs, but I can summarize the difference here - it is only two line:


(--) NVIDIA(0): DFP-0: Internal Dual Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is supported


(--) NVIDIA(0): DFP-0: Internal Single Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is not supported

For what it is worth - the "bad" output is identical to the log output when
there is no cable connected to the card's DVI port at all.

I could not find an option listed in the NVIDIA Readme that would allow me to
force the driver to detect the Dual-Link TMDS.

Obviously, booting with one monitor and switching to the T221 is not feasible,
so I really, really need the driver to work and will be happy to test a beta

Xorg.0.log-verbose-good - log of a good boot connected to another monitor 1st
Xorg.0.log-verbose-bad - log of a failed boot connected to the T221
xorg.conf - conf file, minimal changes from a working Radeon vers

Thank you

netllama 04-23-06 08:25 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
You can try using the ModeValidation X option with the "NoMaxPClkCheck" parameter:

If you need further assistance, please generate and post an nvidia-bug-report.log.


hpcjerry 04-23-06 09:43 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
1 Attachment(s)
Option "ModeValidation" "NoMaxPClkCheck"

made no appreciable difference in behavior.

So, attached are nvidia-bug-report-GOOD.log and nvidia-bug-report-BAD.log

The GOOD is from a run against a 2nd LCD at init, and then manually recabling to the T221 - which produces a viewable display.

The BAD is from a run that was T221 from start to end - and does not produce a viewable display.

PS - the forum's 100K limit on attachments is too small, I had to zip up the nvidia-bug-report.log files in order get them to fit in the 100K per file limit.

netllama 04-23-06 10:06 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
How did you obtain the 1920x1200 modeline?

I'd like to see what is being detected for the EDID. Please remove the UseEDID and ConnectedMonitor options, and generate a new bug report.


hpcjerry 04-23-06 10:38 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
I can tell you right off that NO EDID value comes back from the T221 monitor -nada zilch, nothing. The driver considers it a CRT if the ConnectedMonitor is removed. I even tried the read-edid utility from that guy in Germany and it too fails to read the EDID.

Like I said in the original post, the Modeline comes straight from the config file used with the Radeon 8500 - no change was made. I have had to go back to the machine with the Radeon 8500 for now and the T221 continues to work just fine with the very same Modeline.

Furthemore, the Modeline WORKS if the non-T221 monitor is connected to the 7900GT at initialization and then the cables are swapped. Please acknowledge that you understand this key point, I can elaborate further if needed.

I spent all weekend narrowing this down - and going back and forth recabling is not an easy task because half the time I am flying blind - the only difference is the dual-link vs single-link TMDS reporting. The 7900GT is a dual-link card, so there is obviously something wrong if the driver is reporting it as a single-link TMDS.

hpcjerry 04-23-06 11:24 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
1 Attachment(s)
Attached is the Xorg.0.log with logverbose 6 with UseEDID and ConnectedMonitor commented out. Here are some relevant details pulled out and the entire file is attached.

(WW) NVIDIA(0): No connected display devices detected; assuming 1 CRT
(WW) NVIDIA(0): Unable to read EDID for display device CRT-0


(--) NVIDIA(0): CRT-0: 400 MHz maximum pixel clock
(--) NVIDIA(0):
(--) NVIDIA(0): --- EDID for CRT-0 ---
(--) NVIDIA(0):
(--) NVIDIA(0): No EDID Available.
(--) NVIDIA(0):
(--) NVIDIA(0): --- End of EDID for CRT-0 ---

hpcjerry 04-27-06 07:53 PM

Re: 1.0-8756 fails to detect internal dual-link TMDS on 7900GT
Where is the official place to go to get support from Nvidia for Linux driver problems?

It has been 3 days with no response here, not even a "we are opening bug report" nor has my email to linux-bugs@nvidia.com garnered a single response - not even "we got it and it is in the queue to be looked at."

I've got over $600 worth of brand new nvidia hardware here that was purchased SOLELY on Nvidia's reputation for good linux support. So far, I have not seen anything that even resembles support, so I am forced to conclude that I am looking in all the wrong places. Where are the right places?

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