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Old 07-19-07, 04:09 PM   #1
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Join Date: May 2005
Posts: 5
Default Sync problems on 2nd twinview DFP display

Hi, I'm looking for some insight into this problem. I'm especially interested if nVidia has tested this configuration.
One Geforce 880GTS
Two Dell 3007WFP 30" Flat-panel displays connected with Dual-Link DVI cables (confirmed by looking at the full array of pins)
Intel Core 2 Duo, Redhat Enterprise Linux 4 WS update 5 (64-bit)

I have the two displays set up with TwinView oriented top and bottom, with Xinerama enabled. Always on the "second" monitor (plugged into the right-hand DVI port on the card when viewing it from behind) there is sometimes graphical corruption/artifacts/sync problems. It's hard to describe, but if you imagine the display made up of many "columns" of pixels, the columns seem to be interleaved in a strange way.. like if normally you'd see ABCDEF, it appears as BADCFE. Sometimes the "rows" of the screen shimmer or shake left-to-right, like there are some sync problems. If I reverse the cables, the problem moves to the other monitor. I have an identical setup that also has the same problem, so I don't think the displays, cables, or cards have some individual problem. Remember this happens often, but not all the time. Sometimes the second monitor will look fine. If I kill X, or simply switch to a text console (ctrl-alt-1, then ctrl-alt-7) and back I can sometimes see these graphical errors.

I've tried Linux drivers 1-9755 and 100.14.11 both with the same effect.

My xorg.conf is a pretty vanilla TwinView config. here's the device section
Section "Device"

	Identifier  "Videocard0"
	Driver      "nvidia"
	VendorName  "vendor nVidia"
	BoardName   "Nvidia 8800 GTS"
	BusID       "PCI:01:0:0"
	Screen      0
	Option	    "TwinView" "True"
	Option      "DynamicTwinView" "False"
	Option      "MetaModes" "2560x1600 +0+1600, 2560x1600 +0+0"
	Option      "AllowDDCCI" "True"
	Option      "ConnectedMonitor" "DFP,DFP"
	Option      "TwinViewXineramaInfoOrder" "DFP-1,DFP-0"

Is there a known issue with the 8800 GTS (or similar) that means it can't drive two 2560x1600 displays with TwinView? my Xorg.0.log doesn't show anything immediately wrong...

(II) Setting vga for screen 0.
(**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32
(==) NVIDIA(0): RGB weight 888
(==) NVIDIA(0): Default visual is TrueColor
(==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
(**) NVIDIA(0): Option "ConnectedMonitor" "DFP,DFP"
(**) NVIDIA(0): Option "TwinView" "True"
(**) NVIDIA(0): Option "MetaModes" "2560x1600 +0+1600, 2560x1600 +0+0"
(**) NVIDIA(0): Option "TwinViewXineramaInfoOrder" "DFP-1,DFP-0"
(**) NVIDIA(0): Option "AllowDDCCI" "True"
(**) NVIDIA(0): Option "DynamicTwinView" "False"
(**) NVIDIA(0): Enabling RENDER acceleration
(**) NVIDIA(0): TwinView enabled
(**) NVIDIA(0): ConnectedMonitor string: "DFP,DFP"
(II) NVIDIA(0): NVIDIA GPU GeForce 8800 GTS at PCI:1:0:0 (GPU-0)
(--) NVIDIA(0): Memory: 655360 kBytes
(--) NVIDIA(0): VideoBIOS:
(II) NVIDIA(0): Detected PCI Express Link width: 16X
(--) NVIDIA(0): Interlaced video modes are supported on this GPU
(--) NVIDIA(0): Connected display device(s) on GeForce 8800 GTS at PCI:1:0:0:
(--) NVIDIA(0):     DELL3007WFPHC (DFP-0)
(--) NVIDIA(0):     DELL3007WFPHC (DFP-1)
(--) NVIDIA(0): DELL3007WFPHC (DFP-0): 330.0 MHz maximum pixel clock
(--) NVIDIA(0): DELL3007WFPHC (DFP-0): Internal Dual Link TMDS
(--) NVIDIA(0): DELL3007WFPHC (DFP-1): 330.0 MHz maximum pixel clock
(--) NVIDIA(0): DELL3007WFPHC (DFP-1): Internal Dual Link TMDS
(II) NVIDIA(0): Assigned Display Devices: DFP-0, DFP-1
(II) NVIDIA(0): Validated modes:
(II) NVIDIA(0):     "2560x1600+0+1600,2560x1600+0+0"
(II) NVIDIA(0): Virtual screen size determined to be 2560 x 3200
(--) NVIDIA(0): DPI set to (101, 101); computed from "UseEdidDpi" X config
(--) NVIDIA(0):     option
My instincts say "sync problems" given what I see on the second monitor. nvidia-settings -q RefreshRate tells me 59.86 Hz for both monitors. I've gone through the whole nvidia README and haven't found any settings that help.

Any ideas?
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