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.
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Jamahl - Tuesday, September 8, 2009 - link
Digusting! How much money did intel bung you for this disgrace?strikeback03 - Tuesday, September 8, 2009 - link
How is that disgusting? It is the stock configuration of the processor. They are not doing all this testing as an e-pissing contest of who has better performance per clock, it is a comparison of retail products in real-world applications. If (and according to the review, when) AMD has something similar, I'd imagine they will test with that turned on too.Jamahl - Tuesday, September 8, 2009 - link
Why not benchmark the Phenom 2 with fusion for gaming anand???Gary Key - Tuesday, September 8, 2009 - link
"Why not benchmark the Phenom 2 with fusion for gaming anand??? "Have you actually tried using Fusion with Windows 7 x64? It is a total mess. I will be happy to show some results with it, most will say DNF, but that might not make you happy. ;) That said, AMD is working on it, especially trying to get it to play nice with AOD.
In the meantime, here is the current list of items to watch out for - http://game.amd.com/us-en/drivers_fusion.aspx?p=3&...">http://game.amd.com/us-en/drivers_fusion.aspx?p=3&... .
Jamahl - Tuesday, September 8, 2009 - link
What? It's AMD's fault that an unreleased 64-bit os is causing issues with their software?How many people are using Window 7 64 bit who visit this website?
Gary Key - Tuesday, September 8, 2009 - link
It is just as bad in 64-bit Vista. I imagine a fair amount of people that visit the site are using the RTM version of Win7.Jamahl - Tuesday, September 8, 2009 - link
were you benchmarking a processor at 2.66 gigahertz or a processor at 3.2 gigahertz?Gary Key - Tuesday, September 8, 2009 - link
Do you and SnakeOil live in the same house or is the IP address just that similar? LOL.. The processors were benched as they come out of the box. For Lynnfield that means turbo was on as we stated in the article and here in the comments. For Bloomfield, that also means turbo was on, just as it comes out of the retail box.If you check all the other reviews on the web at the main sites, everyone tested with turbo on in the primary benchmarks. So I guess you can say there is a huge conspiracy between us to actually utilize the processors as Intel intended for the users.
Apparently, we all failed at covering it up, so congratulations on discovering the Freeturbomasons. A now not so secret fraternal organization bent on world domination through the use of turbo frequencies inside processors carrying the blue "i" logo.
For the AMD Phenom II x4 series, they were benched with all cores enabled just as they come out of the box, even though you can disable each core in the BIOS just like you can disable turbo on the i7/i5. I guess to make things fair, we should disable the cores on the 965 BE as having that "feature" turned on is cheating.
Anyway, thanks for making my day, I needed some much deserved laughter. :)
Chlorus - Tuesday, September 8, 2009 - link
Seeing as how Fusion isn't even out yet, that would be hard to do...go troll somewhere else. What is with the idiots coming out of the woodwork on this post? You've got the standard fanboys, as well as insecure LGA-1366 owners who feel the need to defend their purchase, and insecure purchasers of 1156 products who are afraid their choice might be bested in a benchmark somewhere.Roland00 - Tuesday, September 8, 2009 - link
Would you please rerun page 9 with an overclocked 975 and the 870. I am wondering how much the difference will grow when the gpus are fed more information due to the faster cpus. Something like 3.8 to 4.0 ghz on both cpus with turbo off (a good overclock yet not in the unreasonable area)If you are investing 400+ dollars in gpus, and you are building it yourself you are probably going to overclock.