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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JonnyDough - Tuesday, September 8, 2009 - link
Anyone who buys a $1000 CPU has more money than brains. If you wait six months you can buy a newer budget processor for about 1/15 of the cost, overclock it and obtain the same result. I would think that $925 would be more valuable to someone with sense than bragging rights for six months. I was taught that when people brag they are vain morons. A person's value should not be estimated by the stuff they have, but by the choices they make. We all get a lot in life, it's what you do with it that sets you apart. Unfortunately our society is ruled by greed and capitalism. I choose to speak against that. If you have a problem with that, I suggest you take it up with the greedy capitalist complaint department. They don't care either.max347 - Wednesday, September 9, 2009 - link
Hmm, it would seem to me that someone who has $1k to spend on a cpu probably has "alot of brains", hence the better-than-average financial position, enabling the purchase in the first place.Also, you equate greed to capitalism. This is clearly false. People get what they work for in a capitalist society. I am not saying it is perfect, though what would be a better alternative? People are not going to be financially equal, as some work harder than others. To dispute this would demonstrate a lack of experience...to say the least.
Someone chooses to get the best. It's their money, their choice. But you're right, you should probably call them a greedy capitalist.
fullcooler - Wednesday, September 9, 2009 - link
wow, you said that way calmer than I would have. very classy reply to a young leftist. perhaps when obama passes the "free $1000 cpu's for lazy punk leftists" plan, you and I can pay for his cpu,and he wont be a sellout to the man by working for it.imaheadcase - Tuesday, September 8, 2009 - link
I hate people who used that phrase "Has more money than brains". Doesn't it stand to reason, they have brains..if they have more money than you to buy the CPU... lolJNo - Tuesday, September 8, 2009 - link
Not necessarily - they might have inherited the money for example.Maybe you have more money than brains too...
JonnyDough - Tuesday, September 8, 2009 - link
Yep. These people sound like they have no idea how to be frugal with money. It's ok though, a fool and his money are soon parted.lyeoh - Thursday, September 10, 2009 - link
Stop doing that ok?If you discourage too many rich/stupid people from buying the bleeding edge stuff it just makes it harder for the rest of us.
Poor folks like me need those rich guys to rush out and buy the expensive CPUs (and GPUs etc) and work all the bugs out, get the production line ramped up etc.
Then 6-12 months later we have good and cheap stuff to buy.
The best CPU costs way less than an expensive house anyway, so it's not like he's going to cause some sort of nation wide or global financial crisis.
VaultDweller - Tuesday, September 8, 2009 - link
Maybe they don't know how to be frugal with money.Maybe they don't NEED to be frugal with money.
Sure, a fool and his money are soon parted - but so is a brilliant rich man who has more money than he needs.
niva - Tuesday, September 8, 2009 - link
I disagree with your first statement. There are people who simply want the best/fastest and will pay the money for it. Only in the last 3 or 4 years has top of the line performance become relevant only for gaming. A few years ago all sorts of pros needed the fastest they can get their hands on and purchases like $1k per CPU were actually justified.Now just because you can't afford a 1k CPU and never have been, doesn't mean people who buy such things are morons. Same goes for buying a Ferrari by the way. Quit being a jealous putz, thanks!
JonnyDough - Tuesday, September 8, 2009 - link
When you compare value ratios, yes. A $1000 CPU is soon worth about $75. A Ferrari sold as parts is worth about 1/15 of the price also. I didn't think I'd have to spell it out for you.