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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Ben90 - Tuesday, September 8, 2009 - link
Was reading it pretty casually thinking it was just a preview because i didnt think the NDA lifted yet.... then i saw a next page... looked at the tab and it has like 20 pages OMGOMGOMGOMG!!! ITS OUT LOL....Im gonna try really really hard to read the article before i go to the gaming performance though...prolly wont make itLashek - Wednesday, September 9, 2009 - link
you compare it to the Q6600 a lot in the text, but no comparison with an overclocked Q6600 is made in the benches...If you have figures of an overclocked Q6600, could you add them? all over the web these question are asked but business leaders who own these web sites dont want to challenge a overclocked core 2 duo,and quads,or is it politics?
coldpower27 - Thursday, September 10, 2009 - link
You will have to compare an overclocked I750 or i860 to the Q6600 as that would only be fair, no sense doing a stock vs overclocked comparison.It is well known you can equal todays stock performance by overclocking to some degree, but if your going to compare overclock then you need to overclock both processors.
Q6600 will be destroyed by i750 and i860 if you compare perf/watt however.
Joshaze - Wednesday, September 9, 2009 - link
Anand,When testing World of Warcraft what processAffinityMask value where you using?
The default value for this variable does not take advantage of all cores on the Core i7 processors.
Here is the article discussing the CVAR: http://forums.worldofwarcraft.com/thread.html?topi...">http://forums.worldofwarcraft.com/thread.html?topi...
The value should be 255 for 8 cores and 15 for 4 cores.
If not, any chance you could retest using the above values and report back on any changes?
Googer - Wednesday, September 9, 2009 - link
The lack of PS2 is a real deal killer for me, I have a beloved IBM Clicky Model M keyboard (1391401) and I will not give it up for anything. I know PS2-usb keyboard adapter exist but they just don't work very well.I am not alone, there are tens of thousands of vintage keyboard lovers out there and the IBM Model 1391401 is one of the more popular ones among keyboard aficionados.
Kind of sad that a 20-30 year old keyboard still works as well as they day it was made, new cheaper keyboards are less acuurate, uncomfortable, very flimsy and are poorly made. You would be lucky to get 5-6 years out of 'some' of these newer $90+ keyboards.
Save PS2, keep it alive. PS/2 has less lag than any USB keyboard I have tried. There are a lot of great keyboards still in use. There is no shortage of real estate on the back IO shields, so there should be no reason not to include a PS/2 port..
MamiyaOtaru - Thursday, September 10, 2009 - link
Seconding this. USB is incapable of providing n-key rollover for keyboards. PS2 can. Not everyone needs that, but I won't do without it.Zoomer - Wednesday, September 9, 2009 - link
I saw at least one PS2 port on these motherboards. What are you talking about again? Yes, they seem to be shared with the PS2 port for mice, but mice work the same on USB anyway.Taft12 - Wednesday, September 9, 2009 - link
This is probably the most off-topic post I've seen on this site. Fortunately for all of us, your rant is invalid and you never have to say anything about this ever again:http://www.syba.com/index.php?controller=Product&a...">http://www.syba.com/index.php?controller=Product&a...
boogerlad - Tuesday, September 8, 2009 - link
where't ta152h now? That idiot is finally done trolling.snakeoil - Wednesday, September 9, 2009 - link
all the results of this review are biased because they were made with turbo enabled, that's at least 600 mhz overclocking.to be fair you must compare this results against a phenom 2 overclockded at least 600 mhz
people is not stupid.