Hello all, i'm actually testing any 9600BE, and i'm experiencing a strange Phenomen

My 9600BE overclocks better when it's hot.
With my Thermaright 90 ultra with fan 13x200 is a no go, vista won't boot (cpu temp is around 40° idle).
When i unplug the fan the temp is raising to 70° idle so i can boot @ 2.6ghz
The best frequency i can boot is around 100° idle, and vista boot @ 2.7Ghz.
Anyone can try to increase the temps and see if the overclock is better ?

I assume it's really strange ...