I was doing so for this purpose: I could not get my current dual-head AGP card to work. I had cloned screens and when I tried to set it up for dual-head, both screens looked like this. -->
Which is pretty in a way, but not useful.
It seems that Linux, and specifically Ubuntu Lucid, has taken X out of Xorg and put it into the kernel for more speed. They call it KMS, and for your nominal case, it's a good thing. When working with cloned monitors, I was able to get the pretty Compiz stuff working, like transparent terms that show the term underneath. That's sexy right there. It just sucked for my Radeon video card.
And here I must confess a dumbass attack. Consider this sample code they suggest for turning off KMS.
echo options radeon modeset=0 < /etc/modprobe.d/radeon-kms.confI tried that, and because I wasn't in root, it didn't work, so I used vi. And when I went back to check
/etc/modprobe.d/radeon-kms.confit read like this.
echo options radeon modeset=0Of course it was confused by the
echoin there. But now it works fine. Yay me.