P35-dq6 Problem With Mch Voltage> +0.2

[EreK]

Hi

I have the P35-DQ6 DDRII rev1 board and a Q6600 CPU. All the high quality components and impressive CPU PWM design + silent pipe makes it run super cool and ideal for quad core overclocking. So its a great board.


But there is this annoying problem with GA P35-DQ6 when overclocking. Everytime the MCH voltage is set to > +0.2 (0.25 for example) usually after a reboot the PCIEX16 will electronically scale down to PCIEX1 as reported in CPU-Z/Everest and also visible by heavy decrease in graphics performance. I tried F4 / F5 and F6 bios. Restarting the system or shutting down/powering back up doesnt solve the problem.

If you set the MCH voltage to +0.2 or lower it works fine and never falls back to PCIEX1.

It has been confirmed by many GA P35-DQ6 owners that overclock their CPU including me.

Is GIGABYTE aware of this problem? Do they have a plan to fix it?

You can easily recreate the issue I described above.

It works like a switch:

MCH V > +0.2===> PCIEX16 falls back to PCIEX1
MCH V =< +0.2 ===>PCIEX16 works fine.

The problem is you may need more than +0.2V on MCH to have a stable overclock .


To make things clear what I mean by the PCIEX16 slot is the upper most (closest to the CPU) PCIE slot.

Thank you.

[GIGABYTE - Janus Yeh]

Hi EreK

I guess maybe that is because you + too many mch voltage.
sometimes when we over mch voltage, we also need to over PCI-E voltage to make it better, Could you try to over PCI-E voltage at the same time?

Thank you

Janus

[EreK]

Hi EreK

I guess maybe that is because you + too many mch voltage.
sometimes when we over mch voltage, we also need to over PCI-E voltage to make it better, Could you try to over PCI-E voltage at the same time?

Thank you

Janus

Thank you for the reply.

Good point Janus.

Yes I tried setting PCIE voltage to +0.2 and +0.25. Also I tried setting the PCIE bus frequency from 100 to 120. You may get one lucky system boot to windows with PCIEX16 but after a reboot it jumps back to PCIEX1.

Here is all the voltage settings I use:

417x9


PCIE Freq:105-120
Vcore:1.5875
PCIE Voltage: +0.2
VDIMM: +0.35
FSB Voltage: +0.35
MCH Voltage: +0.2 (works good) MCH Voltage: +0.3 (PCIEX1 problem)

[GIGABYTE - Janus Yeh]

Dear EreK

I talked this with our RD, yes this will have this issue in p35 chipset MCH Voltage limited .
sometimes when over MCH Voltage: more than 0.2v, your system can even search no VGA card. we suggest you can just +0.2v for overclock. if you want overclock more, you can over Voltage for cpu, ram..., it will be better.

[EreK]

Thanks for the explanation Janus.

So it's an Intel P35 chipset limitation. Unfortunately I found out that my overclock is not stable with MCH at +0.2. I need more than that to run my CPU at 417x9 fully stable. So I guess I have to move on to an X38 mainboard.

Thanks again for taking time and getting the information from gigabyte RD team.

Regards,

[robin44]

Could you try to set your PCI-E Frequency at 101 or 110Mhz with MCH at +0.3 ? It seems to be the solution to this problem according to other forums...