As you probably already know, AMD's latest addition to the HD 6900 series lineup, the dual-GPU Radeon HD 6990 card, features a dual BIOS switch. Unfortunately, there are a few confusing things as, for now at least, there is no official statement on the warranty regarding the BIOS switch.
The switch is covered with a rather large yellow sticker that points you to the user manual, which then takes you to AMD's website here that gives detailed information regarding the BIOS switch. The only warning, or the only thing that we managed to get from that link is that you have to make sure that your system meets all the minimum system requirements.
AMD labels the BIOS switch position one as 450W Extreme Perfromance BIOS and the position 2, which is the shipping position, as the 375W factory-supported Performance BIOS. The confusion starts when AMD talks about warranty. The warning, among other things, states that :"AMD does not provide support or service for issues or damages related to use of an AMD graphics card outside of specifications or in excess of factory settings. You may also not receive support or service from your system manufacturer."
As far as we are concerned, the BIOS position 2 is still a "factory setting" and not user programmed. On the other hand, AMD might want to distance itself from any other system damage that may happen if you switch it to Extreme BIOS, like for example blowing up your PSU.
We are still waiting for partners and AMD itself to give us the official stand regarding the BIOS switch and we honestly hope that AMD will play its cards right with this one. So stay tuned.