The 8xxxM Radeon GPUs are supported in the latest Linux Beta (13.8, http://support.amd.com/us/kbarticles/Pages/AMDCatalyst13-8LINBetaDriver.aspx ). As this is a beta, it is not a certified release, but it should be usable in the supported distributions. Of course, certain hardware restrictions may also factor in if you are unable to get these drivers installed (certain manufacturers like Sony, Samsung, Panasonic, Fujitsu, and Toshiba want to be the exclusive source for drivers, so our drivers may not work on those systems).
The web team has been advised to update the Release Notes, but can you get the Device ID for your hardware? The easiest way is to run atigetsysteminfo.sh from the Terminal, and the device ID will be under [fglrx] vendor: 1002 device: DEVICEID (4 hex digits). That will be the easiest way to check if your GPU is included in the driver release or not.
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