voltages for E8400 at 4 GHz

[Artas1984]

I need to overclock E8400 at 4 GHz

System:

GA-EP45-EXTREME
Kingston Hyper X 2X2 Gb 1066 MHz DDR2 C5
Enermax Modu82+ 690 W EPS12 V

CPU settings: 9X 445 MHz FSB
RAM settings: default

CPU vcore: 1.4 (default 1.3)
CPU termination 1.3 (default 1.2)
CPU PLL: 1.6 (default 1.55)
CPU reference: auto (default 0.76)
CPU reference2: auto (default 0.8)
MCH core: 1.2 (default 1.1)
MCH reference: auto (default 0.76)
MCH/DRAM reference: auto (default 0.9)

I take it ICH is the south bridge, there fore i can leave it be.
Do i need to correct some of my settings?

 

[doz]

VCore to 1.375v, LLC enabled (may need to go higher, but 1.375v should be enough to atleast boot and start stability testing, may be able to lower, but may have to raise).
CPU Term Id leave at auto for the time being till you get stable and adjust later if need be.
PLL, same thing. AUTO until you find stable settings, fine tune later
MCH Core go w/ 1.225v (might be able to lower later, but Gigabyte boards seem to need a bit more than Asus, 2 boards I had experience with).

Make sure to set your dram voltage to its spec as well.

 

[Artas1984]

I know i should set vcore minimal at 1.4 actually, as 1.375 - 1.385 are the lowest stable vcore values for 1 GHz overclock. I am not worried about temps, because of the really great cooler. Now i have read, as mentioned that PLL, if left at default, should not cause trouble - in fact i have read that some people even lower it, although i've read too that increasing it helps with high FSB values, but i have read that Intel does not recommend above 1.575, so perhaps 1.55 will do. I've read some people use a horrendous 1.7 for PLL.

Is this true that CPU reference voltage should be calculated by vcore X 0.66? So in my case i should set it to 0.92? What about MCH reference?

 

[redduc900]

You can basically leave both CPU and MCH Reference voltages on Auto until you hit a FSB of ~500MHz or higher. Gigabyte CPU Ref is usually a fixed % of CPU Termination (Vtt), and they use 63.33-63.5% as the default value for Ref1 = 0.76V/1.20V (Vtt); GTL vREF ratios of approximately 0.635 (Ref1), 0.648 (Ref2) and 0.617-0.633 (MCH Ref). The CPU Ref and MCH Ref both scale as the CPU Termination (Vtt) is increased, this w/ both CPU and MCH Ref voltages set to Auto. And at a FSB of only 445MHz, just leave CPU PLL on Auto or 1.55V.

 

[Artas1984]

A now i see, so basically important are then only the cpu and northbridge main voltages..

 

[redduc900]

Yes... and Termination Voltage (Vtt).

 

[SupaMonkey]

I don't have that motherboard but my vcore is at 1.38 after the vdroop (=1.4125 in bios).

This is stable 24/7.

 

[Artas1984]

OMG, i realized what was the problem.

I was setting way too low MCH voltage. I have read the forums and saw people setting 1.5 or 1.6 volts on MCH when using 45 nm parts, and i just did 1.2.

 

[wibujo]

My UD3P/E8600 (OC'd 4.27GHz 450x9.5) only needs 1.328v (1.35v bios) Vcore and 1.10v MCH core. This has been 24/7 stable for 18 months. Has never crashed or locked up - even while gaming. 48 hr. Prime 95 Blend / 24 hr. small FFT / 24 hr. large FFT / 25 pass LinX stable. I'm also running 8 gigs or RAM @ 1200 MHz. I would not run MCH core @ 1.5v. for 24/7 use. "NEVER"
Thanks wibujo

 

[Artas1984]

WOW, that is sick! You are lucky to have a stable rig!

 

[doz]

OMG, i realized what was the problem.

I was setting way too low MCH voltage. I have read the forums and saw people setting 1.5 or 1.6 volts on MCH when using 45 nm parts, and i just did 1.2.

You should NOT be using 1.5 or 1.6v on the MCH. Where did you read that? That is quite high...... Maybe on an NVidia chipset (not positive on that even though) but definitely not on a P45 based board.

MCH should be around 1.3-1.4v for a Gigabyte board to be stable to around 500 FSB and possibly more depending upon your board. With a 445 fsb you shouldnt need more than 1.3v though really (unless you are utilizing 4 memory slots).

 

[SupaMonkey]

I don't know what the hell MCH is, but i can tell you that i haven't changed it.