Intel's Core i7 870 & i5 750, Lynnfield: Harder, Better, Faster Stronger
by Anand Lal Shimpi on September 8, 2009 12:00 AM EST- Posted in
- CPUs
Overclocking: Great When Overvolted, Otherwise...
Back when I asked Intel why anyone would opt for LGA-1366 over LGA-1156 one of the responses I got was: overclocking. The most overclockable CPUs will be LGA-1366 chips.
We tried overclocking three different CPUs: the Core i7 870, Core i7 860 and Core i5 750. We overclocked using two different coolers: the retail low profile HSF and a Thermalright MUX-120 (the heatsink Intel is sending around to reviewers for high performance testing). I'll get one thing out of the way: the retail heatsink pretty much sucks for overclocking:
| Intel Core i7 870 | Max Overclock (Turbo Disabled) |
| Intel Retail LGA-1156 Cooler | 3.52GHz (160MHz x 22.0) |
| Thermalright MUX-120 | 4.20GHz (200MHz x 21.0) |
The Thermalright enables higher overclocks by removing heat quickly enough allowing us to increase the voltage to the CPU. While roughly 1.35V is the limit for the retail cooler, The Thermalright MUX-120 let us go up to 1.40V. In both cases you need to have a well ventilated case.
Um, yeah.
Now for the actual overclocking results. We overclocked in two ways: 1) with turbo mode enabled and ensuring stability at all turbo frequencies (both single and multiple cores active), and 2) with turbo mode disabled simply going for highest clock speed.
The results are in the table below:
| CPU | Stock Clock Speed | Max Overclock (Turbo Enabled) | Max Overclock (Turbo Disabled) |
| Intel Core i7 870 | 2.93GHz | Default: 3.39GHz (154 x 22.0) 3C/4C Active: 3.70GHz | 4.20GHz (200 x 21.0) |
| Intel Core i7 860 | 2.80GHz | 3.23GHz (154 x 21.0) 3C/4C Active: 3.54GHz | 3.99GHz (210 x 19.0) |
| Intel Core i5 750 | 2.66GHz | 3.2GHz (160 x 20.0) 3C/4C Active: 3.96GHz | 3.92GHz (206.5 x 19) |
For best performance with all four cores active, disabling turbo mode is the way to go. Otherwise you have to reduce the BCLK in order to make sure your system is still stable when the one-active-core turbo mode kicks in. For example, with our Core i7 870 with turbo disabled we hit 4.2GHz using a 200MHz BCLK. If we used the same BCLK but left turbo enabled, when only one core was active we'd hit 5.4GHz - clearly not realistic with only air cooling.
The benefit of leaving turbo enabled is that you get a more balanced system that's not always using more power than it needs to.
The Core i5 750
Our Core i7 860 sample wasn't that great of an overclocker
Breaking 4.2GHz with our Core i7 870
At roughly 4GHz overclocks for all of these CPUs, it's reasonable to say that they are good overclockers. But how about with no additional voltage and the retail heatsink?
| CPU | Stock Clock Speed | Max Overclock, Turbo Disabled (No Additional Voltage) |
| Intel Core i7 870 | 2.93GHz | 3.37GHz (22 x 153MHz) |
The stock overclocks just plain suck on Lynnfield, you need added voltage to overclock the chip. With more voltage it works just like a Bloomfield or Phenom II, but at stock voltages Lynnfield just doesn't clock very high. And it has nothing to do with yields.
Facebook
Twitter
RSS
343 Comments
View All Comments
snakeoil - Tuesday, September 8, 2009 - link
and the cherry on top of the piecore i5 750 and core i3 don't support virtualization.
http://www.virtualization.info/2009/07/intel-core-...">http://www.virtualization.info/2009/07/intel-core-......
that's fantastic, colossal intel.
what's wrong with intel
Anand Lal Shimpi - Tuesday, September 8, 2009 - link
Intel VT-x is supported by the Core i5 750:http://processorfinder.intel.com/details.aspx?sSpe...">http://processorfinder.intel.com/details.aspx?sSpe...
Take care,
Anand
snakeoil - Tuesday, September 8, 2009 - link
sorry incomplete linkhttp://www.virtualization.info/2009/07/intel-core-...">http://www.virtualization.info/2009/07/...core-i3-...
AssBall - Tuesday, September 8, 2009 - link
What are you talking about? These overclock FINE; read the article. 4 Ghz. Anyone that is gonna overclock bloomfield or lynnfield seriously is opting for an aftermarket HSF, so don't bother arguing that. Your comment doesn't make any sense.TA152H - Tuesday, September 8, 2009 - link
You missed the point.When you overclock the processors, you change the characteristics of turbo mode. Consequently, the big advantage of the Lynnfield disappears, and they run at the same clock speed, instead of the Lynnfield at a higher clock speed.
Do you understand now?
eternalfantasy - Tuesday, September 8, 2009 - link
lolemogoinginstyle - Tuesday, September 8, 2009 - link
"There are better sites that have answered these questions. I used to like this site, but this review is another disappointment. "Just how is that Tom's Hardware gig working out for you? I noticed your name was not on any of their launch reviews since you seem to be an expert on the subject. Why is that?
TA152H - Tuesday, September 8, 2009 - link
Thanks for asking.When I have time, I will be writing another article, which they hopefully will use, but to be honest, the time it takes to write an article, at least a well-written one, takes an enormous amount of time and effort.
Getting and verifying data is only part of it. Writing it in an artistic an interesting way is very time consuming, and, at least for me, requires many rewrites of the same pages. Each page took me at least five hours, some many more, plus the upfront time of deciding which pages to write, which probably took at least 30 hours of research.
The editor of Tom's wrote their articles, and it's clear to see the much more thorough review he did. Personally, I like him and occasionally do communicate with him, and I probably would like Anand too, since he seems like a good fellow, but I have no real affiliation with their site. If I write an article they like, they might publish it. That's it.
But, honestly, if you do it for money, you're a fool. It takes WAY too much time for that. You really have to want to do it, and the money is secondary.
goinginstyle - Tuesday, September 8, 2009 - link
So it took you five hours a page to do a copy and paste from Wikipedia on that so called article of yours? I read the Tom's P55 article, not seeing how it was any more thoughtful than the one here or at Tech Report. At least Anand did some searching and reported on items like PCIe clocking/voltage requirements that I noticed was not mentioned at Toms.Your only motive for these posts is to try and look impressive at Toms in hopes that they will publish another boring piece of dung from you. Otherwise, your complaints here are just as justified at Toms or TR, yet you are not posting at either site. That is why it is so obvious as to what you are up to with the flame bait comments.
TA152H - Tuesday, September 8, 2009 - link
I never even looked at Wikipedia, since I don't consider it a valid source of information.Why do you talk about things you don't know about. In fact, some people used Wikipedia to argue some points with me. I made a point never to look at those pages.
But again, what have you done with your, except produce carbon dioxide and speed up global warming? You seem pretty worthless to me.