Problems with GTX580 under cold

[K404]

Ok, I am GTX580 noob... I played with reference card in January and only now am I playing with a CuII

On the stock cooler, things are looking fine. average 975MHz core, 1325MHz GDDR

On cold... things get bad

Vantage GT1 is terrible...... the score doesn't scale with MHz?????? Tried different drivers, 32 and 64 bit, different PCI-E slots and PCI-E MHz. Doesn't scale with CPU power. TBH..... it almost feels like the more I push the core, the worse the FPS get. Score gets worse if I drop the GDDR clocks, so I don't think its data corruption


Vantage GT2 is fine though??????


3DM11 is totally fine, so it can't be coldslow?

3DM06 and GT03 are also writeoffs.... I only played at those for a very short time, I decided to stop before I wasted more LN2

Unigine scales very very slowly. (can only run on XP. W7 = stage 9 hang )




Any ideas guys?



Thanks



A random idea about the memory..... 1325MHz is fine with the stock cooler and 1.70vGDDR. I increased it to 1.75v under cold..... everyone else appears to be running much higher vGDDR for lower or similar clocks. Does my card have a cherry IMC or is this related to my problem?