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Old 07-19-07, 04:09 PM   #1
racalac
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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.
Setup:
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
Code:
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"

EndSection
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...

Code:
(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: 60.80.13.00.02
(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?
Thanks.
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