Dell XPS 630i PCI-E problem (x8 @ 1.1 instead of x16 2.0)
I'm the owner of Dell XPS 630i with q6600 processor. I bought it with 2 graphic cards: ATI Radeon HD 3870. I decided to sell this cards and I bought 1 Radeon HD6950 2 GB (ASUS) and i installed it in PCI-Express x16 card slot (PRIMARY_GFX_SLOT1) (17).
I also have got installed sound card in PCI card slot (SLOT 6) (13).
Everything works, but the problem is that this PC support PCI-E x16 2.0, Radeon HD6950 is full compatible wth PCI-E x16 2.0 too, but when i run GPU-Z, or look at the info in catalyst control centre i see information, that bus interface is x8 1.1
Dell's motherboard: Both PCI-E x16 slots are irreversibly locked in hardware to 8,8,1,1 which means that single graphics card users are only receiving half the PCI-E lanes (8 as opposed to 16). As a result, users are left with significantly less graphics performance, especially for utilization of more advanced graphics card upgrade options and performance already on the market.
This system was meant for running two graphic cards and with that configuration you would probably not see a significant performance hit like you may running a newer card in single mode. Your board is 1.1 not 2.0 and there is nothing you can do about this or it running at the x8 speed outside of replacing the motherboard.