GTX670 Tri SLI
3930K stock
16gb DDR3
GPU gets 23000
CPU gets 13000
Combined 2800
GTX670 Tri SLI
3930K stock
16gb DDR3
GPU gets 23000
CPU gets 13000
Combined 2800
Wild guess: GTX 670 SLI support in drivers is unfinished? The combined test is a very complex job for multi-GPU drivers...
Alternatively you could be throttling due to the PSU getting maxed out. Combined test places the highest load on the power supply as it maxes out CPU and GPU(s) simultaneously (the rest of the tests either push the GPU or the CPU but not both at the same time)