website has posted a modded version of AMD's drivers that will turn an ATI Radeon HD 2900XT into a FireGL V8600.
This might not be all that useful to most owners of a Radeon 2900XT, but if you're into OpenGL 3D rendering and need a fast card for the previews, then a Radeon HD 2900XT will be a lot cheaper than a FireGL V8600 card.
Considering that the FireGL V8600 will set you back US$1899, while you can pick up a 1GB Radeon HD 2900XT for as little as US$499.99, you can save quite a bit of money this way.
You can download the modded drivers here
and it's about a 70MB download.