let me explain with te bios flasing what happened step by step , i have the normal sappire core 900 mem 1050, i then found out that HIS made an exact reference card but had core 920 and mem 1120 and i flashed it in DOS mode atiflash -p -f HIS6870.bin and it all worked perfectly for 8 monts or so, i then saw that sappire made a Toxic edition with 970core and mem 1150 and that flash is what made all things wrong, first i saw that the card wouldnt boot but fortunatly i had a X1800 lying around and flashed it back to the original sapphire bios which i saved even before going with the HIS bios 8 months or so ago, and it came back to life and worked, but then i realized that some games ran slow or slower, and decided to run 3Dmark 11 and scored 3700 instead of the usual 4400, i started to freak out since i thougt it was the VGA card and tried re-flasing it with the SAPPHIRE and later with the HIS one and still scored low having no problems with boots and 2D all seemed fine even Bluray i thougt maybe it was the OS and reinstalled windows 7 and still low scores arrrggg and ten it came to me, maybe the pci-e has gone to 8x or 4x and decided to look for a solution but meanwhile to support my theory is that i moved the video card to the second pci-e 16x and scores and games went back again to normal.
if its just config, pcie dont have a speed adjustment as AGP had, in GPU-z says its still 16X, another question, is 6870 crippled in a 8X lane or would it have to go to 4X to see that diference, i ask cause my brother has a 6850 and maybe if its 8x i can still go crossfire but with the 6850s what u think