Update at 2007-09-17: You can nowadays just do an apt-get install fglrx-driver fglrx-kernel-src, then start from point 2 of the installing sequence.

This is a small howto to get the ATI fglrx driver working on your Debian [sid] installation. As of 8.25.18 the driver finally supports Xorg 7.0

The steps

Foreplay

• Go to ATI's support page and download the latest driver for you platform [mind whether you are on 32bits or 64bits]
• The filename will be something like: ati-driver-installer-8.25.18-x86.run , where 8.25.18 is the driver version and x86 your platform
• Copy this file to a dir like /usr/src
• Run it: sh ati-driver-installer-8.25.18-x86.run
• It'll ask you about what you want it to do; choose "create packages for my platform"
• Choose to create Debian packages [of course]
• Agree with the license
• Enter some installation path [/ is fine, enter /tmp/blah if you don't need ATI's install log and license file]
• Check Debian packages
• Choose the Debian flavour you're on
• When it's finished, it'll have generated various .deb's
• If you haven't got module-assistant installed, do that now: apt-get install module-assistant

Installing

1. Install fglrx-driver_xxx.deb and fglrx-kernel-src_xxx.deb
2. m-a update
3. m-a prepare
4. m-a
5. SELECT and check fglrx-kernel
6. Follow the steps in the screen
7. Be sure to install the driver when asked
8. Done!

Well, you're done installing the driver. Try modprobe fglrx now. If it complains about version magic and an Invalid module format, purge all fglrx-* packages from your system [apt-get --purge remove fglrx-* and try again]. Edit your /etc/X11/xorg.conf and change the Driver entry in the Device section to "fglrx". Restart X.

Now you can check whether it works: run glxinfo and check whether direct rendering is enabled, and whether ATI is doing that for you [glxinfo | grep direct]. fglrxinfo should give you some more info. Of course, you can test with glxgears too, but as this isn't a benchmark -- which you should be aware of -- but rather a testing tool, you have to start it with -printfps.