Symptoms:
Removing one card (disabling card 2 via the pcie switches) causes the system to be stable again.
Testing the card in slot 2 by itself reveals the card is 100% stable when run on its own
Testing the power supply (Lepa 1600W) reveals no problems
putting all 3 cards back in and enabling it, the instability returns. Precision X also crashes reliably (driver throws error, sometimes recovers, sometimes system crashes instead..)
I disabled GEN3 in the bios and it seems to have solved the problem.Not all games are affected (League of Legends was fine even with 3 way SLI enabled)
Dirt 3, Battlefield 4, and NFS Most wanted were all impacted.
I am running on the latest beta drivers for battlefield 4, but it was not stable on the release drivers either.
Motherboard Asus ROG Rampage IV Formula x79
CPU Intel i7 4820k Ivy Bridge-E @ 4.6ghz
GPU(s) 3 WAY SLI -- EVGA GTX 680 SC Signature (2GB)
Displays 5140x1050 @ 120hz using 3 x Samsung 2233RZ
RAM 16 GB 2133mhz G.Skill RipJaws Z
PSU LEPA G Series G1600-MA
Case Cooler Master Cosmos II Ultra
Storage Vertex 3 256 (Games), Intel 320 Series 128 (OS), + 4TB HDD