Do you have desktop effects enabled and a very high cpu usage with this chip set? If so, disable desktop effects.
Then try to edit your /etc/X11/xorg.conf in order to get a better performance. In the subsection "Display" you should have
the entry "virtual". Minimize the defined resolution or delete the entry. Don't forget to save the xorg.conf before you edit it.
I believe in everything, except humans.
LM9, Debian Testing Xfce, Debian Sid Xfce - CPU/Amd64 2,6Ghz, Graphics/Nvidia 9600 GT, Sound/SB Audigy4 emu10K1