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Enterprise Linux and state-of-the-art hardware: a difficult marriage

A customer bought a Dell Precision T7500 recently. Beautiful machine, awesome power, running CentOS5. The videocard in the machine was the first I ever saw with nothing but DisplayPort connectors: no old-style VGA, no DVI, no HDMI. At first, a 1680x1050 screen was connected using a DisplayPort-to-DVI connector, and that worked flawlessly.
But in came a new beast: a 30-inch 2560x1600 screen. The standard DVI cable can't handle this resolution, and neither can the DisplayPort-to-DVI connector, so even a dual-link DVI cable doesn't solve this issue. And I'm sure you'll agree: running such a beauty at 1920x1200 seems a waste.
I tried connecting the monitor directly using a DisplayPort cable, which can easily handle the maximum resolution, but the EL5/CentOS5 xorg-x11-drv-ati driver is too old: version 6.6.3 (with some backports from 6.12.2) doesn't detect DisplayPort-connected monitors correctly. Compiling a newer driver isn't easy, because the newer ones require Xorg 1.2 or 1.3, not the 1.1 version in EL5.
So until EL6 comes out (later this year, we expect), I'll need another solution. A three year old NVidia card I had lying around still had a real dual-link capable DVI output.
Replace the card, boot the machine, /etc/X11/xorg.conf gets updated to use the "nv" driver, and the GDM login screen comes up in ... 1920x1200. RTFM translated to "man nv" in this case. After reading the manual page, add
Option "AllowDualLinkModes" "true"
to the Device section of /etc/X11/xorg.conf, restart gdm (init 3; init 5), and voila.

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