Intel i7 920 - Finding The Sweet Spot

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Hyperthreading: Does it really give that much back? What’s the best Speed/Power Savings?

Hyperthreading: Does it really give that much back? What’s the best Speed/Power Savings?

Let’s start off with Hyperthreading:

Does it really pay off using it? Yes and No.

First off – Yes.

For any task that uses multiple cores you should see an advantage in using it, although in my experience it seems to be limited to certain applications, such as folding and rendering apps. In rendering apps, for instance 3D Studio Max, I can see speed increases ranging from 20 to 40%.

Then we have the No – Gaming.

This is where I noticed it BIG time. Actually at first I was shocked and thought I did something wrong. It took a couple days but after I thought I was going crazy, I started running more tests in X3: Terran Conflict, getting more detailed information and coming up with this:

3.8 GHz w/ HT = Average 75.9 fps

3.2 GHz w/ HT = Average 70.9 fps

3.4 GHz w/o HT = Average 86.4 fps

3.8 GHz w/o HT = Average 93.1 fps

Currently I run at: 3.66 GHz w/o HT = Average ~90.5 fps

Then I saw a test from a fellow OC Forum member: 4.2 GHz with and without HT on, running 2x GTX275’s SLI, and he came up with results of 98.3 fps… for both!

I know this game loved ATIs from my past experience, so I’m not sure what’s going on here. But the FPS seems right on for the clock speed that it’s running, give or take a little. I never did get around to true testing in other games but I did notice Crysis was faster. Sadly, I haven’t had time or played much of anything else since then.

Moving on to Speed/Power Savings.

I know everyone wants to hit high overclocks – 4.0 GHz, 4.2 GHz, 4.5 GHz with HT enabled. That’s all wonderful, just DO IT! Have a nice stable system at that speed, but really is it necessary to run it there?

Increasing clock speed might not give you a 1 to 1 return in programs or games you run, so you could run a few tests, play around a bit and come up with a well rounded speed for typical activities and every once in a while when you need the power, crank that CPU up. While I don’t have a kilowatt meter but observing max heat versus average use heat, I noticed some good results.

Originally I was pushing my i7 920 C0 to 3.8 GHz w/ HT. She was a cooker, pushing nearly 80C full load with an average of 68-72C (winter/early spring loads). Yet my voltage wasn’t much at just 1.225V BIOS (1.27-1.28V load Windows). When playing around with HT above to give my results, I also started tweaking clock speed and voltage. Now I sit at 3.66 GHz w/o HT with load temps of 68-70C (summer) and an average around 55-59C.

Not only is my voltage down to 1.1475V, I can drop it further as I have not yet hit bottom. I also enabled SpeedStep to further help keep it cooler using less power. I only recommend doing this after your system is stable at the speed you want it, as my results might not work for everyone.

In conclusion, you can get a little more speed disabling HT when gaming, and with some tweaking you might be able to shed some heat from the system and save a little power as well. Tweak the system to what you want it to do daily, then switch to your maximum settings when you really need the extra power.

This Thread in OC Forums is common talk with CPUs these days.

Deathman20 in Overclockers Forums

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