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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Gary Key - Wednesday, September 9, 2009 - link
Actually the manufacturers wanted Clarkdale desperately for the school/holiday shopping seasons. It is delayed as they are still debugging the platform, unofficially I think that means the drivers are not ready. ;) Believe me, if we had a stable Clarkdale platform worthy of a preview, you would have read about it already.justme2009 - Wednesday, September 9, 2009 - link
You are incorrect sir. The manufacturers were complaining to Intel that they couldn't get rid of the current stock before Intel released mobile Nehalem, so Intel caved.http://techreport.com/discussions.x/16152">http://techreport.com/discussions.x/16152
http://www.techspot.com/news/33065-notebook-vendor...">http://www.techspot.com/news/33065-note...-pushing...
http://www.brighthub.com/computing/hardware/articl...">http://www.brighthub.com/computing/hardware/articl...
http://gizmodo.com/5123632/notebook-makers-want-in...">http://gizmodo.com/5123632/notebook-mak...o-delay-...
Needless to say, I'm waiting for mobile Nehalem (clarkdale/arrendale). With a 32nm manufacturing process, plus starting in 2010, Intel will begin to move both the northbridge and southbridge chips onto the processor die. The move should complete some time around 2011 as far as I can tell.
It will be far better than what we have today, and I'm really ticked off at the manufacturers for holding back progress because of their profit margin.
Gary Key - Wednesday, September 9, 2009 - link
I spoke directly with the manufacturers, not unnamed sources. The story is quite different than the rumors that were posted. I will leave it at that until we product for review.justme2009 - Wednesday, September 9, 2009 - link
Of course the manufacturers wouldn't fess up to it. It's bad business, and it makes them look bad. It already angered a great many people. I don't think they are rumors at all.justme2009 - Wednesday, September 9, 2009 - link
Personally I'm holding off on buying a new system until the northbridge/southbridge migration to the processor die is complete, ~2 years from now. That will definitely be the time to buy a new system.ClagMaster - Tuesday, September 8, 2009 - link
“These things are fast and smart with power. Just wait until Nehalem goes below 65W...”I surely will Mr Shimpi with this exceptional processor. I am going to wait until the summer of 2010 when prices are the lowest, rebates are the sweetest, before I buy my i7 860. By that time, hopefully, there would be 65W versions available on improved stepping. It’s worth the wait.
I would wager the on-chip PCIe controller could use some additional optimization which would result in lower power draw for a given frequency.
Intel sure delivered the goods with Lynnfield.
cosminliteanu - Tuesday, September 8, 2009 - link
Well done Anandtech for this article... :)ereavis - Tuesday, September 8, 2009 - link
great article. Good replies to all the bashing, most seem to have misread.Now, we want to see results in AnandTech Bench!
MODEL3 - Tuesday, September 8, 2009 - link
Wow, the i5 750 is even better than what i was expecting...For the vast, vast majority of the consumers, (not enthusiasts, overclocking guys, etc...) with this processor Intel effectively erased the above 200$ CPU market...
I hope this move to have the effect to kill their ASP also... (except AMDs...) (not that this will hurt Intel much with so many cash, but it is better than nothing...)
I see that the structure/composition in this review and in many others tech sites reviews is very good, maybe this time Intel helped more in relation with the past regarding info / photos / diagrams / review guide etc...
One question that i have (out of the conspiracy book again...) is,
if the integration of the PCI-Express controller in the CPU die on the mainstream LGA-1156 platform will be a permanent strategy from now on...
and if the recent delay for the PCI-Express standard 3.0 has a connection with the timing of the launch of mainstream LGA-1156 based CPUs with PCI-Express 3.0 controller integrated...
Sure, they can launch future LGA-1156 motherboard chipsets with PCI-Express 3.0 controller, but doesn't this contradict the integration strategy that Intel just started with the new processors?
MODEL3 - Tuesday, September 8, 2009 - link
I can't edit...I just want to clarify that the PCI-Express 3.0 question is for LOL reasons, not taken serious...