Re: RHEL4, 7800GTX, SLI (only one GPU detected)
Looks like it's detecting the link width at 16x. Unless you have one of the newer nForce4 SLI x16 chipsets, it's possible that you just didn't set the motherboard to SLI mode. Most SLI motherboards have a paddle that must be inverted to support SLI.
What motherboard do you have?
"Physics is like sex. Sure, it may give some practical results, but that's not why we do it." - Richard P. Feynman