Dell 2405FPW on Linux and Xorg

I've just got my Dell 2405FPW, a 24" 1920x1200 widescreen TFT display with a Samsung PVA panel, and it's awsome. Endless space on the desk (Acrobat can show two A4 pages side by side, and the table of contents left to it), sharp, bright, fast (neither Tuxracer, Quake 3A nor HD Video shows any blur, confirming the 12ms/16ms switch times in the spec). Note that LCDs always blur when you follow some small spot (e.g. mouse cursor) with your eyes, since the LCD is "always on", while a CRT flickers. This problem might be solved in future, with LED backlights, which however will bring us back flickering.

You should keep at least 60cm (24") away, because at that distance, the individal pixels don't show up, and the contrast is still perfect in the corners. So far, there's only one defect green subpixel in the lower right corner (which took me days to find it), and one close to the center of the top (found after two months - I hope the screen won't degrade more).

Configuring under Linux with Xorg and DVI-D orignally was a bit difficult. There was no appropriate default 1920x1200 modeline, and the display is a bit picky in that mode. It wants exactly 60Hz, and the pixel clock must be less than 170Mhz (DVI-D limitation). However, after trying several modelines found on the Internet, one of them did work. I later found out that the monitor reports a valid modeline via DDC (nv driver), and this even works better, so this is what I've in my XF86Config (er, xorg.conf):

Modeline "1920x1200"  154.128 1920 1968 2000 2080  1200 1203 1209 1235 -hsync -vsync

at least with the nvidia binary driver (I've a GeForce 5600FX).

My GeForce FX 5600XT seem to have some problems with hsync during movies (single lines move a few pixel to the right and back at random). I see this problem on VGA (when using VGA only), and a bit less worse on DVI when I use DVI only. I have no such problem with a GeForce 6600 at work.

The solution for me is to set the "TwinView" option so that both VGA and DVI carry the same image. This seems to cure the problem. Add the following to the "Device" section:

        Option "TwinView"
        Option "HorizSync"   "DFP-0: 30-81; CRT-0: 30-81"
        Option "VertRefresh" "DFP-0: 56-76; CRT-0: 56-76"
#       Option "MetaModes" "DFP-0: 1920x1200, CRT-0: 1024x768 @1920x1200"
        Option "MetaModes" "DFP-0: 1920x1200, CRT-0: 1920x1200"
        Option "ModeValidation" "DFP-0: NoMaxPClkCheck,NoEdidMaxPClkCheck"
        Option "TwinViewOrientation" "Clone"
        Option "ConnectedMonitor" "CRT-0, DFP-0"
        Option "XvmcUsesTextures" "true"

This solution creates another problem: Syncing. For OpenGL, the solution is quite easy: Set the following variables in your .bash_profile:

export __GL_SYNC_TO_VBLANK=1

And with the nvidia-settings program, under "X Server XVideo Settings" turn off all Sync options.

The NVidia drivers after 7174 and before 8756 (with OpenGL 2.0) don't allow my GeForce 5600XT to go past 140MHz on the DVI line. Fortunately, 8754 introduces the "NoMaxPClkCheck" option (see above) to work around that problem. The newer driver also recognises the mode line via EDID fine, and allows synchronizing to the DFP screen. The drivers in between worked on the GeForce 6600 at work (limited to 155MHz).

A few other programs need additional configuration: Add the following line to your .mplayer/config for correct aspect ratio:


There are some negative points, though:

I bought another seven panels for the office (in my function as sysadmin). The panel is the ideal size and resolution for EDA CAD stuff.

Created 02apr2005. Last modified: 10aug2011 by MailBernd PaysanPGP key