I have just noticed, that when i am playing games like bzflag that use 3d acceleration, the cpu usage jumps to about 100% and the game jerks every few seconds. the same happens with glxgears, except without jerking. i look down the process list, and there is nothing taking up more than 20%. I also notice this with glx screensavers, and the same cpu usage thing happens. I am using a chaintech geforce 6800 128 meg card. i never had this problem before. i believe it started when i upgraded the nvidia drivers. I have done a "glxinfo | grep rendering", and that gives a yes for direct rendering. i have an amd athlon 64 3700+ and i am on FC6.