From what I can tell, the ATI Proprietary Linux Driver doesn't support this card. Basic support for the card may be already in the kernel. You may want to look into the Video for Linux
project, they may have something.
You may want to ask ATI directly, here
Other possible helpful sites: LinuxTV
In my opinion (and many others) ATI's support for Linux is atrocious. NVidia is quite good, even though they only release proprietary drivers.