Originally Posted by AaronP
That's why I made that option disabled by default. At boot, your GPU is not running at a high enough clock frequency to be able to drive that mode. On some GPUs, the VBIOS aggressively underclocks the card to conserve power and reduce heat, relying on the nvidia driver to raise the clocks later as needed. Unfortunately, clock programming is very complex and slightly dangerous, so the nv driver doesn't even try. I'm afraid that if you want to use that mode, you'll need to use the full nvidia driver.
Isn't there a way to tell the nv driver what frequency to use?
I can't use the full nvidia driver because I'm using gentoo hardened with grsecurity patches. That means that code has to be relocatable like PIE and PIC and I don't think the full nvidia driver is built that way with those options. Besides setting the clock frequency for a standard GTX8800 card can't be that dangerous. The monitor specs are known and so is are the GTX8800 specs. So the nv driver only has to deal with the one 2560x1600 mode not a range of other frequencies.
So how do you set the clock frequencies in the nv driver? The nv driver is GPL right so the code is already available as part of xorg. If it already has the settings for the 1280x800 mode all you need is the other mode too.