I've managed to run radeon mobility 7500 with direct rendering (I
have IBM ThinkPad T30 with "such old" ATI card). It raised speed of my
PDP routine from 14 up to 25 fps.
Don't know, if it is 100% correct. Maybe it will help someone with
same card and d:b running on it.
I changed only xorg.conf (MAKE BACKUP BEFORE STARTING AND MAKE SURE
YOU KNOW HOW TO MAKE USE OF IT IF SOMETHING FAIL!).
Cheers
Luke

And here are the changes:
# Section "Device" in the file /etc/X11/xorg.conf:
Section "Device"
Identifier "ATI Technologies, Inc. Radeon Mobility [Radeon Mobility 7500]"
#please remember to change the device name once more few lines later.
Driver "radeon"
BusID "PCI:1:0:0"
Option "XAANoOffscreenPixmaps"
Option "RenderAccel" "true"
Option "AGPMode" "4"
Option "VideoRam" "32768"
Option "AGPSize" "16"
Option "AGPFastWrite" "true"
Option "EnablePageFlip" "True"
Option "UseInternalAGPGART" "no"
Option "backingstore" "true"
Option "AllowGLXWithComposite" "true"
Option "AllowLargeTextures" "2"
EndSection
# Section "DRI" - you should have this by default, "dont ask why"
Section "DRI"
Mode 0666
EndSection
# Add Section "Extensions"
Section "Extensions"
Option "Composite" "Enable"
EndSection