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-   -   cannot compute backend DFP timings (http://www.nvnews.net/vbulletin/showthread.php?t=80534)

zimiq 11-16-06 12:42 PM

cannot compute backend DFP timings
2 Attachment(s)
I try to use my ViewSonic VP201b in 1600x1200 resolution.
First I get only 1280x1024 resolution, then I found this forum and try to add modeline option to monitor section.
Now I have only 800x600 resolution and when I read Xorg.log and I found error message like title, it seems to come to when validating modeline, nvidia-bug-report-06111900-01.log line 2056.

Is there any way to get this working.

netllama 11-16-06 12:47 PM

Re: cannot compute backend DFP timings
You've set the ModeValidation option to reject every type of mode. I'm not sure why you're doing that, but its not a good way to debug the original problem.

However, according to the EDID in your display, you need a 162Mhz pixelclock to run with the native 1600x1200 mode. Your hardware isn't capable of that pixelclock:
(--) NVIDIA(0): ViewSonic VP201b (DFP-0): 112.0 MHz maximum pixel clock

zimiq 11-16-06 01:13 PM

Re: cannot compute backend DFP timings
2 Attachment(s)
Monitor edid data contains:
(--) NVIDIA(0): Detailed Timings:
(--) NVIDIA(0): 1600 x 1200 @ 60 Hz
(--) NVIDIA(0): Pixel Clock : 162.00 MHz
(--) NVIDIA(0): HRes, HSyncStart : 1600, 1664
(--) NVIDIA(0): HSyncEnd, HTotal : 1856, 2160
(--) NVIDIA(0): VRes, VSyncStart : 1200, 1201
(--) NVIDIA(0): VSyncEnd, VTotal : 1204, 1250
(--) NVIDIA(0): H/V Polarity : +/+
This data shows when edid enabled.

I make modeline with that data, but it does not work.
Monitor works 1600 x1200 resolution with Ati card.

Cambo 11-16-06 01:18 PM

Re: cannot compute backend DFP timings
Possibly, the line below the one quoted by netllama is more telling;


(--) NVIDIA(0): ViewSonic VP201b (DFP-0): Internal Single Link TMDS
Having not had any exposure to DVI stuff, I cannot really help you any more than just highlighting that line.


netllama 11-16-06 01:24 PM

Re: cannot compute backend DFP timings
Right, the pixelclock that the 1600x1200 mode requires is 162Mhz:
(--) NVIDIA(0): Pixel Clock : 162.00 MHz

Your hardware is only capable of 112.0MHz. That is further underscored by the fact that your hardware is only Internal Single Link TMDS capable (as Cambo noted).

This isn't a driver bug, its a hardware limitation.

zimiq 11-16-06 01:38 PM

Re: cannot compute backend DFP timings
How can 1600x1200 resolution work with Ati card and windows, if this is hardware fault.

Cambo 11-16-06 02:10 PM

Re: cannot compute backend DFP timings
The ATI card quite possibly has a Dual Link TMDS output, giving approximately double the Pixel Clock frequency.


netllama 11-16-06 02:25 PM

Re: cannot compute backend DFP timings
Because the problem is the videocard.

Cambo 11-16-06 02:37 PM

Re: cannot compute backend DFP timings
Quite possibly, your card was designed to only have Single Link TMDS - that is a decision made by the manufacturer, not Nvidia.

I have a Geforce FX 5700LE from XFX, and from the look of the output in my nvidia-bug-report.log, it would seem to support much higher Pixel Clock frequencies;


(II) NVIDIA(0): NVIDIA GPU GeForce FX 5700LE at PCI:2:0:0 (GPU-0)
(--) NVIDIA(0): Memory: 131072 kBytes
(--) NVIDIA(0): VideoBIOS:
(II) NVIDIA(0): Detected AGP rate: 8X
(--) NVIDIA(0): Interlaced video modes are supported on this GPU
(--) NVIDIA(0): Connected display device(s) on GeForce FX 5700LE at
(--) NVIDIA(0):    PCI:2:0:0:
(--) NVIDIA(0):    EIZO FlexScan F67 (CRT-0)
(--) NVIDIA(0):    OEC (CRT-1)
(--) NVIDIA(0): EIZO FlexScan F67 (CRT-0): 400.0 MHz maximum pixel clock
(--) NVIDIA(0): OEC (CRT-1): 400.0 MHz maximum pixel clock

You may well need to buy a more capable video card to get the higher resolutions that your monitor is capable of.


netllama 11-16-06 02:48 PM

Re: cannot compute backend DFP timings
Actually, you're using CRTs which are almost always 400Mhz. Only DFPs have lower pixelclocks.


Cambo 11-16-06 02:59 PM

Re: cannot compute backend DFP timings
Heehee. I suspected something like that. I gather the difference is due to the fact that CRTs use an analog signal, as opposed to the digital signal for DFPs.

Actually, that may be worth looking into, zimiq. You may be able to use a DVI-VGA converter with your card/monitor. You will lose a little image quality, due to the digital->analog and analog->digital conversions, but you should be able to run your monitor at it's highest resolution.

I'm sure Lonni will correct me if I'm wrong there ;-)


longshot 11-16-06 05:51 PM

Re: cannot compute backend DFP timings
Single link DVI is supposed to be able to do 1600x1200@60Hz with GTF blanking. Ref http://en.wikipedia.org/wiki/Dvi wikipedia :) The graphics card otoh ...

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