SLI slower than single gpu.

[jtsanda]

Hello. I just recently bought two xfx 8600gt's off of craigslist. It is the XXX version and it has GDDR3 with clocks very close to that of an 8600 gts. So after I overclocked it myself, I'm now basically running 2 8600gts's. The problem is that no matter what I do my games run around the same, if not worse, in sli than it does in single gpu mode. In Oblivion in particular, I get about 25 fps in a certain spot with sli and 27 in the same spot without sli enabled. I turned on the SLI Visualizer in Nvidia's Control Center and it appears that at that certain spot, it is a cpu bottleneck.

My Specs:
Athlon 64 3800+ (single core) oc'd to 2.8ghz 512kb L2 cache
2gb DDR-2 OCZ SLI Ready memory (667 @ 709mhz)
60gb Seagate Barracuda IDE UltraATA 7200RPM HD for windows
and
320gb Western Digital SATA 5400RPM HD for Games
2 xfx 8600gt's XXX Edition OC'd to 700/1456/900 (very stable) GDDR3
EVGA 590 sli Motherboard (2 16x pcie lanes in sli mode instead of standard 8x)
550wtt Cheiftec PSU

So if I bought the Athlon 64 5600+ x2 Brisbane model cpu would that alleviate the cpu bottleneck in my games? I'm also running sli without the bridge connector. If I bought one of those, along with the new processor would SLI then be faster than the sinle card?

Sorry for such a long post. Any help is appreciated.

 

[belial2k]

yes, you need the sli bridge. yes, an old single core processor is going to bottleneck even the weaker of more modern graphics cards.

 

[jtsanda]

I knew it probably sounded obvious, but I just wanted to make absolute sure before I spent more money on this. Thanks!