Screaming Penguin - Source Does Matter

Carmack has a sit down with Beyond 3D and boy is it a good read.

Since the P-A guys had to have the nerdy pull quote, I will follow suit:

The ARB2 path uses a lookup that exactly matches the bias / square calculations used by the NV10 / NV20 / R200 paths so the surfaces look the same in the different rendering modes.

B3D also notes at the end of the article:

We'd also like to add that id's Marty Stratton has informed us that they're working on the Linux client and it will be made available as soon as possible.