VERY bad perfomance on 8800 GTX 768MB

[Terr1]

I just bought a XFX 8800 GTX 768MB graphics card to replace my NVIDIA 7950 GT card.

However I get a VERY poor performance testing games and 3dmark06, the score and performance is worse than my 7950 GT card?

Windows Vista 64-bit..
Tried the newest beta/non beta x64 NVIDIA driver.. same results.

My specs:
CPU Type DualCore Intel Core 2 Duo E6600, 3484 MHz (9 x 387)
Motherboard Navn Asus P5B Deluxe (3 PCI, 1 PCI-E x1, 2 PCI-E x16, 4 DDR2 DIMM, Audio, Dual Gigabit LAN, IEEE-1394)
Grafikkort NVIDIA GeForce 8800 GTX (768 MB)
1x WD Raptor disc and 2 x 500 GB in SATA RAID
1x DVD-RW drive

Seasonic S12-II 500W PSU


Any idea's what could be wrong? PSU not strong enough?

 

[chizow]

Most likely a PSU/GPU System Sentinel issue or a motherboard issue with PCI-E lanes allocated. It'd help if you ran a diagnostic like GPU-Z and report your card clock speeds and PCI-E lanes.

 

[imported_wired247]

I'm thinking massive cooling problem or not enough PCIe lanes.