I7 920 P6T SE overclocking

Hello all. This would be my first foray into overclocking, and I've been doing some research and reading guides on the subject. I think I've picked up the basics pretty quickly but I have some questions that I can't answer on my own. Excuse me if my technical lingo isn't up to par.

Specs:

Core i7 920 (stock cooler)
Asus PT6 SE
6GB OCZ DDR3 1600
CM Storm Scout case

I played with balancing the speed, voltage and heat output for my i7 920. Here are the BIOS settings I eventually came to:

BCLK: 173MHz
DRAM Frequency: ~1033MHz
CPU Voltage: ~1.183V
DRAM V: 1.6V

Idle: ~50C
Load: ~75-80C
(using Prime95 for about 3 minutes @ default 'blender' setting)

I didn't encounter a problem once while adjusting these settings.

The thing that puzzles me is that when I leave everything at auto, which is I assume 1.20V for the CPU, the temperatures are about 5C higher for both idle and load. This seems quite hot to me, based on what I've read, which is why I began reducing the CPU voltage. Shouldn't the default values yield lower temperatures? My case is quite roomy and has three fans.

I didn't want to screw anything up so I reset everything to their default values.

One other question: Lowering the BCLK appeared to reduce temperatures slightly, though I was under the impression that the only thing which affected temperature was the voltage settings. What's up with that? Is it just because the CPU is working at a slower speed?

Thanks ahead of time.

When you set the voltages on auto the mobo tends to put way to much voltage on it when you overclock.

That is why everyone sets it manually.

Lowering the bclock will reduce temperaures. The heat output of a chip is shown by this formula:

TDP_new = TDP * (MHz_new/MHz_stock) * (V_new/V_stock)^2

The tdp is the amount of heat it puts off. For the i7 920 this number is 130w.

You can see by that formula that when you increase the speed it will increase the heat output.

maybe you dont understand what i was sayin.

I said that the motherboard is VERY liberal with the voltages.

Say to run you will only need 1.3v most motherboards will WAY overdo it and give it 1.45v.


Understand now?

Yup, I understand. I guess I was just surprised that the default BIOS settings would be setting the i7 at such a high temperature.

I will be getting a new cooler when I upgrade my system a bit more in the future, but for now it's brand new and my budget has reached its limit. I've heard that the i7 can overclock reasonably on the stock cooler, however, which is why I'm trying it out.

Thanks again.

Ceuper, 80 degrees is a bit too high, so like "overshocked" I recommend buying a new cooler, something like a scythe mugen would be more than enough.
Remember that the p6t se also supports socket 775 coolers.


BTW, you may want to run Prime95 a bit longer than 3 minutes to check stability. One pass, about 15 minutes, should be the bare minimum. I have the same processor, RAM and motherboard and at 160 bclk I needed to increase the cpu voltage to 1.25, the QPI voltage to 1.25 and RAM voltage to 1.64 for the system to make it through one pass of Prime95 (1.20 volt for QPI and CPU wasn't stable, though 1.23ish might be enough but you'll have to test it.) Also don't forget to update the bios, turn off Intel speedstep and set the CPU multiplier at 20.

Of course you may have the D0 version of the i7 920, while I have the C0/C1 version and D0's require somewhat lower voltages, still you can get random crashes if you have an unstable system, so run Prime95 for multiple passes to test stability.

They won't, and you know what, today I found out CPU and QPI voltages of 1.3125V were still stable (with RAM at 1.64V and bclk at 160) Speedstep is better left disabled when overclocking. You can try to turn speedstep back on after you've reached a stable overclock, but it can make an otherwise perfectly stable overclocked system crash (it let's the motherboard adjust voltage and multiplier settings beyond your control.)

75C is still too high (you want to stay under 70C), and temps will only go up when increasing the cpu voltage, reducing the voltages from 1.25V to 1.23125V reduced my load temps from 66C to 62C, that's with my old Scythe Mugen cooler (from a socket 775 system I used to own.) You can get similar decent cpu coolers for under 40euros, so buying one will definitely be worth it.


To measure the CPU temps you want a program like "everest", which has a sensor tab and shows both the CPU temps (the ones we're interested in) and those of the individual cores which are indeed a tad higher.

Well, in my case temps never differ by more than 1C between realtemp and everest, anyway the hottest core runs at 67C during prime95.

The settings I ended up with after some testing were: bclk: 160 (not even supcom or crysis show improved framerates beyond 3200mhz so no need to overclock it further for 99,99% of home users), dram: auto (the board sets it to 1.56V under both idle and heavy loads), CPUvolt: 1.21875V, QPIvolt: 1.21875V, RAM speed: 1282mhz, QPI: 5772.

CPU and QPI voltages at 1.20625V were unstable, even with dram at 1.64.

So this is probably as good as it gets for a bclk of 160, I'm guessing a bclk of 175 requires slightly higher (~0.01V-ish) CPU and QPI voltages.

Sapphire HD 4890.

Not really: http://www.guru3d.com/article/core [...] -review/18 you might squeeze out a few additional frames by overclocking even further, at low resolutions with 3 or 4 gpu's but like I said, 99,99% of users don't have that kind of money or don't think it's worth it.