Last week , i found a post in http://forum.ubuntu.org.cn/viewtopic.php?f=94&t=239467, which told you how to enable 3D acceleration through installing the latest Open Source ATI drivers.So i follow it step by step as bellow:

1. Download kernel *.deb from http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.32/ then install .
2. Restart the computer , select the 2.6.32 entry in the grub menu, then edit /etc/source.list , add the follow two line:
deb http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu karmic main
deb-src http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu karmic main
3. Install
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0x4f191a5a8844c542
sudo apt-get update && sudo apt-get upgrade
4. Restart.

After that , i enter the follow comand to test:
~ > glxinfo | grep render
direct rendering: No (LIBGL_ALWAYS_INDIRECT set)
OpenGL renderer string: Mesa DRI R600 (RV620 95C4) 20090101 x86/MMX/SSE2 TCL

so why direct rendering is no? Does it mean 3D acceleration has not been enabled?
how to solve it ? I didn't install any other ati drivers .

notebook: Thinkpad T400 , ATI Mobility Radeon HD 3470 , Ubuntu 9.10 ,Kernel: 2.6.32-020632-generic

~ > lspci | grep VGA
01:00.0 VGA compatible controller: ATI Technologies Inc Mobility Radeon HD 3400 Series