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Old 06-28-07, 02:28 AM   #1
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Join Date: Aug 2006
Posts: 20
Default edid vs. modeline


in the process of figuring out how to deal with unhelpful EDID information, I came across the following which is a mystery to me. An IBM DFP connected via DVI-D to a 7900GS displays a nice 1280x1024 native resolution image when I set up xorg.conf to use EDID provided information. But when I force the driver (110.14.09) to use a modeline and not edid modes via options, the DFP refuses to show a nice display. I constructed the modeline by letting xvidtune show me the timings when the display works. And xvidtune shows me the same exact timings when the display does not work, and EDID is disabled.

Is there other information except for the timings used to drive the display (except for the content) ? Or does somehow the nvidia driver report timings to X different from what it actually finally uses ?

Here is another hint. When the display works, xvidtune reports a modeline with a 76Hz refresh rate. But the on screen information of the DFP itself says it is displaying at 59.9Hz. When the display does not work, xvidtune still reports the same modeline but now the on screen info of the DFP says it is displaying 640x480 at 59.6Hz.

The underlying reason is that on another display (3dp) I get bad edid information. This other display works when I first start up X with the IBM DFP connected, get a good display and then switch cables. So I would like to preserve that state when I start up X with the other display directly connected. The other display (3dp) does not work when I just use its EDID modes.

Did anybody come across a similar situation ?

Thanks, Andreas
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