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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moronsworld - Saturday, September 26, 2009 - link
To all you morons that don't understand economics. amd gone = intel monopoly = intel processors overpriced. Plain and simple. Take an economy class or 2, you morons. AMD is a good company, just that Intel's processors are better at the moment. God too many morons in this world that are allowed to vote. We live in a society ruled by morons.TA152H - Tuesday, September 8, 2009 - link
Actually, you don't really know what you're talking about.On-die memory controllers are nothing new. The Nexgen 586 had it in the mid-90s. Intel just knew when to add it, and when not to. That's why the Core 2 blows AMD processors away, while being significantly smaller.
AMD instruction schedulers were behind Intel's Pentium Pro from 1995 until the Phenom II came out. It still doesn't have full memory disambiguation like Intel introduced with the Core 2, but at least the memory scheduling is now on par with the Pentium Pro. I'm not sure that something they like brought up though.
64-bit processing is also old hat, and really was just an extension of the 386 protected mode anyway, with a lot of Microsoft input.
The K8 wasn't really much of an architecture, it was a K7 with a memory controller, and a couple of extra stages for better IPC, that most idiots thought was for higher clock speeds. It was a failure, and was what put AMD in the situation where they are now. It was, generally, better than the Netburst, but then, is that such a high bar to get over? The problem was, they actually believed it was a good processor until the Core 2 relieved them of that misapprehension. The reality is, Intel's mobile chips were always better than the K8, but the damn fools made us buy the Pentium 4 for the desktop. To AMD's credit, at least they never made anything horrible like that, but, really, their primary claim to fame was based more on the terrible Intel design than a great processor of their own, and the fact Intel wouldn't let us use the mobile chips for desktops.
JonnyDough - Tuesday, September 8, 2009 - link
Please work on your English before replying to me in the future. Thanks.Aenslead - Tuesday, September 8, 2009 - link
So you *must* have perfect english to reply in these forums?Gosh, never saw that in the Terms and Conditions agreement when I created my account. So that means that anybody (or a nobody, like you) have a say on what other races and people from other countries that don't speak English as their first language, that LIKE READING and giving their opinion in a FREE MOFO OPEN FORUM, must do to post here?
You and your kind are pathetic.
JonnyDough - Tuesday, September 8, 2009 - link
I didn't say anything about having perfect English. You sir, are a troll. I just wanted his reply to be coherent. This is the ENGLISH version of DailyTech, there are other language versions. His post didn't even make sense, and yours was just trolling.ginbong - Wednesday, September 9, 2009 - link
I understood what he said, maybe you need to sharpen up your analytical skills and stop being a dlckhead on this hardware analysis website.Better yet, how about taking the money you have saved for your next PC upgrade and enrolling into Grade 1 again.
dastruch - Tuesday, September 8, 2009 - link
and you don't get it too... patheticjigglywiggly - Tuesday, September 8, 2009 - link
This is a hot cpu, except I want 6 cores + HT. 32nm... quads ahh yeah. I still don't like the i5, because I don't want two sockets on one brand at the same time. It just limits options, I am only looking at i7/i9, because I bought this qx6700 in 2006 for 1000$. It was a good purchase, because q6600s were a while away and they were 500$. I got my qx6700 to 3.85ghz, now it's at 3.5ghz stable. Curse you electromigration! Also curse you economy! I don't have enough money for a 6core+6HT 1000$ cpu again.JonnyDough - Tuesday, September 8, 2009 - link
*Laughs at the moron...Go buy a Ferrari and then wreck it and sell it for parts. That's essentially a larger scale version of what you did.
Lifted - Tuesday, September 8, 2009 - link
Huh? Buying a $1000 CPU is like wrecking a Ferrari?"Laughs at the moron"