Multy GPU Hashing Problem

[BBN]

Alright I am experiencing a very bugging issue. Today I added a second 7950 and started hashing away BUT as soon as the first card starts the khs for the second one dropp by 70-80khs..System specs:

MB:Asrock 970 Extreme4
PSU: Seasonic 750w
VGA: 1 - 7950 Sapphire 2 - 7950 Sapphire Vapor X
8GB 1333
AMD drivers: 13.1

Card N1 is in the main pci and the Vapor is in the second x16 for now. Settings in Guiminer are identical ( 7950 high usage ). Trixx settings:

Card 1: 925GPU/1250M/0.962V - 550khs
Card 2 ( Vapor ) : 925GPU/1250M/0.962V - 560khs

Any ideas?

Thank You

EDIT: I am seeing the load on the 2nd GPU slips to 70% and then back up....Load only varies on the 1st card is working

[dogie]

Possible reasons:

1) Overheating
2) Silly driver
3) A high CPU usage thing just happened
4) Intensity setting not high enough
5) Crossfire being silly, if they are in cf
6) Custom clocks resetting, every time they reset they'll stop hashing for a bit.