Hey everyone. This is my first post. Really grateful there's a community like this to help. And FYI: I'm not posting before spending a week (for about 4 hours each day) having searched threads all over the web for similar problems and attmepting the proposed solutions as well as finding a hundred differrent ways to 'google' the same issue.
Here are my specs:
PSU: 650w (can't remember brand but it's excellent and gets screaming reviews)
MOBO: Gigabyte P55A-UD3
CPU: i5 760
GPU: 2x EVGA Superclocked Signature GTX 680
OS: Windows 7
Nvidia Driver: 310.90
ASUS 23.6 Display (1920x1080p @60hz native)
Sli is not officially supported by my mother-board (as I have a 16x and 4x PCI slots) so I am using "HyperSLI" to access SLI functionality. I have confirmed that the issue I'm having isn't to do with the limitations of the bus speed as I have benchmarked my cards in their respective slots bringing these results:
Gpu 1 8373 x16 slot
Gpu 2: P7966 x4 slot
(approximately a 5% differrence)
I doubt this should be having such an adverse impact.
SLI 3D Mark 11 score:
P11223 -this score seems slightly higher than the common scores for my rig.
I acheived this after:
-disabling USB 3.0 and SATA 6 (to minimize drain on shared PCI resources)
-and setting CPU performance enhancer (in GB BIOS) to Extreme (options being Extreme, turbo and standard) -note these are just presets -they're not any form of overclock.
Metro 2033 has shown a marked improvement from SLI with the GPU usage being in the 70-80 range in 1080p and maxed settings with 4xmsaa -definitely seeing the benefit of 2 cards as opposed to one.
However; Crysis 2, Battlefield 3 and Far Cry 3 are all having a similar issue.
With a single GPU, the usage is around 70-80% and I'm getting what you'd expect from a single GTX 680.
When running SLI, both GPU's usage is around 40-50% and I'm getting the performance you'd expect from a SINGLE GTX 680 still.
By performance I'm referring to Frame rate.
In battlefield 3 on larger maps (all settings maxed 1080p, v sync off, motion blur max, 4xmsAA (ultra) I'm hovering between 70fps and 80 with regular drops to 60s and 50s and occasional (but still often) drops to 40s when looking over a large section of the map.
In BF3 my CPU usage during SLI is up around 75-88%.
I've of course reinstalled the drivers multiple times.