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Old 04-04-04, 10:06 PM   #1
kijiki
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Default Bizzare visual (likely DVI transmitter related) artifacts on second head w/ dual DVI

This is possibly one of the most bizzare problems I've encoutered, either personally or professionally (My day job involves writing an XFree86 driver).

I have a Gainward Ultra/780 XP. This is a dual DVI out FX 5600 card. Both heads run 1600x1200 at 24/32.

First off, a minor problem (quickly resolved). I had to add:
Option "ConnectedMonitor" "DFP,DFP"
to get it to detect and drive the second LCD panel. Unsurprising due to the relative rarity of dual DVI users.

Now the real problem:
The second head gets colored horizontal lines (the color changes, but it is the same for a run of the X server) that rapidly move down the display (top first). I think they may be stippled, but it is very hard to tell because they move so fast. Occasionally, the second head blanks entirely for about a half a second.

The weird part is that it is controlled entirely by the area of the first head covered by a specific color (which color also changes when I restart the X server, though it appears to be unrelated to the color of the lines).

The first time I characterized it, it was 0x0000FF. The more 0x0000FF I put on the screen, the more horizontal flashing lines I got, and if I had enough, the second head would flash black occasionally. If I covered the screen entirely, the second head would flash black and stay that way. Moving the colored window to the second head stopped the problems. Interestingly, 0xFF00FF doesn't cause the problem. I lowered the red channel all the way to 0x2000FF before it started again. 0x2100FF doesn't cause it.

Later, I upgraded to 5336 (I had been using 5328) and the color changed to 0xFFA800. Strangely, it is now even more color specific. 0xFFA802 causes about a 50% response (compared to 0xFFA800). 0xFFA804 causes no problems at all. 0xFCA800 does not cause it, nor does 0xFFA900.

Finally, I restarted my X server, and now it is 0xFF7800.

Turning off hardware cursor (thinking it RAMDAC/DVI transmitter related) did no good, nor did turning off acceleration.

A friend with the same model card sees the same problem using Windows XP. We tried putting it in mirror display mode, to see if the artifacts were actually present in VRAM; the problem persisted on the second head only! Putting the second head on VGA causes the problem to disappear as well.

I suspect it is either a hardware design flaw in the second DVI transmitter, or a driver bug in setting up the transmitter. I know very little about this aspect of driver programming, as the "hardware" I work on lacks a RAMDAC (the VMware virtual SVGA). I am led to believe that the windows and X nvidia drivers share enough code that the existance of the problem on windows and X does not necessarily rule out a driver issue.

Advice welcome, as are stories from others who have seen the problem, or are using dual DVI out without issues!

Thanks.
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Old 07-23-04, 10:12 AM   #2
sehh
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Default Re: Bizzare visual (likely DVI transmitter related) artifacts on second head w/ dual

I'm having the same problem. My second DVI shows horizontal lines.

I'm using Fedora Core 2 with the latest 6106 drivers.

My video card is: Asus GeForceFX 5600 VideoSuite

Monitors: two Sony SDM-X73 TFT 1280x1024
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Old 08-02-04, 09:11 AM   #3
stephen93
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Default Re: Bizzare visual (likely DVI transmitter related) artifacts on second head w/ dual

I do not know whether there is any connection, but I have been seeing annoying artifacts such as red flashing lines with my DVI output (FX5200) but only at 75Hz. Have you tried 60Hz? Did it change anything?
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Old 08-02-04, 01:35 PM   #4
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Default Re: Bizzare visual (likely DVI transmitter related) artifacts on second head w/ dual DVI

Quote:
Originally Posted by kijiki
Advice welcome, as are stories from others who have seen the problem, or are using dual DVI out without issues!
XFX 5700 Ultra dual-DVI. Two Apple 1024x768 displays @60Hz. No problems under 53.03. No problems with VMware workstation 4.5.2.

Quality issues between DVI displays probably stems from Dual-DVI NVIDIA cards having one GPU-integrated transmitter and one external transmitter. While I can't know how your card manufacturer implemented the ports, I suspect that anomalies appear on display connected to the integrated transmitter, and anomalies appear at only certain resolutions that are operating slightly out of VESA spec. Hope that can aim you towards improvement.
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