Intel D975XBX2 and Q6600, which voltages ?

[myg]

I have a Intel D975XBX2 rév 507, last bios at this time (2802), and a quad6600 - G0 stepping. 2x1Gb Crucial Ballistic Tracer PC2-6400 (5.5.5.15 2.12v)

I have a question about vcore. I put the vcore to 1.325, 1.35, 1.4... always the same vcore on CPUz or Everest or bios: 1.3250V. the trends show 1,275 max.

Why ? I think that i can't put over 1.325.

FSB and MCH have the original voltage, and after differents tests, i put 1.4 and 1.6 max. Wrong too.

vDDR2 = 2.20, 2,24, 2.28: wrong too.

Timings: 5.5.5.15 and 266/667 ratio = 4:5

9x350 (=3150 MHz) is wrong with theses differents settings. I test parameter one by one.

But 9x345 (=3105 MHz) works fine. vcore in bios 1.325, vddr2=2,20

Is the fsb limit with Q6600 on 975 ?

I have another system with the same 2x1Gb Crucial ballistic tracer PC2-6400: Gigabyte GA-P35-DQ6 rev1, QX6700@3408 (vcore=1,41, 12x284, DDR2=5:8=454MHz, 4.5.5.13) - Works very good.

I use Thermalright Ultra 120 eXtreme + Artic 12025PWM on Gigabyte, and Noctua NH-U12F + Noctua NF-S12 on Bad Axe2. The PWM on BadAxe2 doesn't work. curious...
Thanks for your help.