Overclocking Intel's Core i5-750 & i7-870

[Rob Williams]

We found out earlier this week that Intel's Lynnfield-based processors are fast, but who said that cranking the clocks to make them even faster was a bad idea? In this article, we take both the Core i5-750 and i7-870 for an overclocking joyride, and the stable overclocks we were able to achieve is nothing short of impressive.

You can read our full report on overclocking Intel's latest processors here and discuss it here!

Turbo Boost will jump 4 bins with 1/2 cores actives on i5-750. On i7-870 it jumps 4 bins with 2 cores active and 5 bins with 1 core active. Have you tested your stability in such scenarios?

[Rob Williams]

Hi Unregistered:

From my understanding (and what I remember), overclocking a Turbo-equipped processor automatically disables the additional boost that the first and second core would see from a light workload. Instead, regardless of how hard you are pushing the CPU, cores 1 - 4 would share the same top-end clock frequency. If you are running the Core i5-750 at 173MHz and 20x in the BIOS, that means that one core or four, would all be using the same frequency of 3.633MHz (because of the 21x Turbo).

I can't verify this right now since I have other benchmarking machines hooked up, but I'm quite certain this is how it's always worked since Core i7 was first launched last fall.

Thank you, I was unaware of this. I'll see if I can find more information or try it out myself since I'm currently building my own i5-750 machine.

[Rob Williams]

I recommend you take a look at the page I wrote on Turbo in our Lynnfield article, as it might clear up a little more on the tech:

http://techgage.com/article/intel_co...e_mainstream/3

You might also want to play around with TMonitor to experiment:

http://cpuid.com/tmonitor.php

Does that mean then that if you're not upping the voltage you could possibly keep the stock heat-sink on it? Because otherwise you would have to take that added cost into the whole performance vs value of overclocking

[Rob Williams]

If the CPU voltage is kept at stock, then a stock CPU cooler would suffice. Upping the CPU frequency does increase the CPU temperature as well, but its effect is nothing close to increasing the voltage.

I have an i5 on the Gigabyte P55 UD5 but the BIOS doesn't allow me to set the multiplier to 21. Am i missing something?

[Rob Williams]

Originally Posted by Unregistered

I have an i5 on the Gigabyte P55 UD5 but the BIOS doesn't allow me to set the multiplier to 21. Am i missing something?

That's the Turbo multiplier, and it's not available in the BIOS. Rather, once you overclock your processor, the multiplier of 21 will take effect on the next reboot if Turbo is still enabled. You can verify this by overclocking, then loading up CPU-Z and seeing if the multiplier does indeed go to 21x, which it should.

on your core i7 870 CPU-Z scree shot it was only showing a voltage of 1.344v, which leaves another .05v for overclocking. If you actually had the 1.4v, you could probably hit 4.2GHz easy....

and also, the i5 can easily run 4.2GHz on that 1.4v, and the reason i know is because i am using one right now to write this!

nice job on the article btw!

[Rob Williams]

Originally Posted by Unregistered

on your core i7 870 CPU-Z scree shot it was only showing a voltage of 1.344v, which leaves another .05v for overclocking. If you actually had the 1.4v, you could probably hit 4.2GHz easy....

Well that's true, but heat comes into the picture at some point for me. I tend to quote the voltage I use in the BIOS, but I need to begin quoting whatever CPU-Z is showing since it's a tad more accurate (as it reads the current real value from the BIOS).

Glad you are successfully running such a sweet clock on your chip

Hey I enjoyed your article...It is nice to be able to get results on one page instead of clicking through 10 pages of ad-ridden geekdom.

Maybe for a conclusion you could do a cost-benefit analysis for a few of the common chips, with and without overclocking and with and without aftermarket coolers.

Would it be possible for you to publish all of the settings you changed on the motherboard for the 3.63 Ghz Core i5 750 overclock? Or did you only change the base-/hostclock?

[Optix]

Boo @ Turbo Boost!

Overclock the old fashioned way!

Yeah, I know. I'm not adding anything to the conversation but you can likely hit higher frequencies overclocking through the BIOS than you can with Turbo Boost provided your cooling holds out.

[Rob Williams]

Originally Posted by Ciddan

Would it be possible for you to publish all of the settings you changed on the motherboard for the 3.63 Ghz Core i5 750 overclock? Or did you only change the base-/hostclock?

The host clock had to be set to 173MHz, that's it. Nothing else was changed. The success of this might vary between motherboards, so setting the voltage manually might be required. Judging by our screenshot, the real voltage was between 1.25v - 1.30v, so if you set it to 173MHz and it's not stable, then try pumping up the voltage manually to one of those values (or in the middle).

Originally Posted by Optix

Boo @ Turbo Boost!

Overclock the old fashioned way!

Of course you can, because Turbo boost isn't the way to overclock, it simply boosts each core by a set amount. It's so easy to overclock way beyond the effectiveness of Turbo. I mean here, all I did was raise the BCLK and I had a brag-worthy OC.