It seems as though with SDK 1.2 and newer all new drivers work... Official support aside, I'd be willing to bet it would work fine for you .
And using windows, embarrassingly enough, you would have a much easier time reverting the version anyhow! :'(
thanks Methylene. This has also been my experience. I plan give it a shot with the 4870, and will post any performance issues. I remember reading on some posts about occasional performance degradation on some newer releases.
Yes, windows have better driver support, since the gaming community tends to be non-linux non-opensource... This is why I am sticking for now with Windows x64
OK. Using HD4870, the ATI driver 8.11 on Windows XP x64, plus the SDK 1.2.1 gave me the same performance numbers I got from ATI driver 8.8 plus SDK 1.2
I used a gather kernel for test written in Brook+