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Another new element to the Core i7 is the Quick Path Interconnect that we mentioned earlier. This high-speed interface connects the processor (or processors, in a multi-proc machine) to the chipset. Intel currently has two QPI speed iterations. The Core i7-965 Extreme Edition runs at 6.4 gigatransfers per second and the non-Extreme chips, such as the Core i7-920 and Core-i7-940, run at 4.8GT/s.
The QPI is important to watch because ramping it up too far can kill your overclock. For example, pushing the base clock from its stock 133MHz to 200MHz on a Core i7-920 means that the QPI will default to 7.2GT/s. That’s quite bit more speed than the stock 4.8GT/s; however, we successfully tested a Core i7-920 running at 7.2GT/s and believe that’s still within the realm of viability.
The QPI speed of the Core i7-920 and Core i7-940 is derived by multiplying the base clock (133) by 36, which equals 4788 or 4.8GT/s. The Core i7-965 uses a default QPI multiplier of 48, but unlike the non-Extreme chips, the 965’s multiplier is not locked. If you believe your overclock is failing because you’ve cranked the QPI too far, you can try dropping the speed by changing the QPI multiplier. On some overclocking runs with a Core i7-965 Extreme Edition, we had to drop the QPI back from 7.68GT/s to 7.04GT/s to increase reliability. The bad news is that you can’t do this with the budget chips.
Turning off the CPU VR Current Limit Override in the BIOS prevents the CPU from throttling back the multipliers under the Turbo Mode. Notice the lack of Turbo Mode tuning versus that with an Extreme Edition installed.
You probably learned as a three-year-old not to mess with electricity after that incident with the wall socket. The dangers of electricity haven’t changed, but to wring the greatest clock speed out of your CPU, you’re going to need to overvolt the suckah. Actually, it won’t be just the CPU—our highest reliable overclock was only achieved by upping voltage to the CPU and parts of the chipset.
How much is too much? The default core voltage of the three current Core i7’s is 1.2 volts. We were able to push voltage to 1.5 on a budget Core i7-920 and successfully make it through some torture testing, but in our opinion, that’s probably too much juice (at least with air cooling). Sure, it ran our stress tests for a reasonable amount of time, but we don’t think the chip will live for long. A more reasonable voltage is probably 1.4 volts (just slightly more than the maximum allowable of 1.375), but take that with a grain of salt, too. Because your CPU, motherboard, cooling, and PSU will be different, the amount of voltage you can add will likely vary from our scenario.
Another area you’ll have to overvolt is the QPI interface. You’ll likely have to increase the voltage from its stock 1.1 to 1.3 to get a reliable overclock. Some folks recommend running QPI voltage at or above the CPU’s core voltage, but we didn’t have to on our budget chip as it was happy with 1.3 volts. Our Extreme Edition, however, needed 1.5 volts to the QPI, which was equal to the CPU voltage. Finally, you’ll have to add voltage to your RAM to get it to higher speeds. There has been chatter that a RAM voltage exceeding 1.65 can destroy a CPU— fortunately, most of the high-performance DDR3 binned for Core i7 doesn’t seem to need more than 1.66 volts to run, which is certainly within reasonably safe limits.
Sometimes the highest clock isn’t the best for performance with Core i7. Using Turbo Mode, we saw a 3.66GHz chip perform as well as one running at 3.80GHz, and without the excess heat and voltage.
Overclocking and cooling go hand in hand. If you can keep the CPU cool, you’ll increase your overclocking limit. For the majority of our testing, we used a beefy ThermalRight 120. As good a reputation as this cooler has, it’s still just an air cooler. Water cooling is an even better choice for overclocking as it’s more efficient at removing heat from the core. Better still would be an exotic phase-change or Peltier unit that could bring the CPU temps far below zero degrees Celsius.
What’s a safe temperature for Core i7? That’s also open to debate. We had to dig around the Internet to find that all three Core i7s have a maximum recommended temp of 67.9 Celsius. That, however, is the maximum temperature taken on the outside of the heat spreader with a calibrated thermistor. In English, that means that if you’re being told that all four cores are running 82 C under full load, you’re probably OK for the short term—but your chip probably won’t last five years. It would be wise to aim for 80 C or lower, and even better to run in the 70 C range. Just remember that you may have to crank it all back in the summer.
If your head isn’t spinning by now, you’re in good shape, but most people, even somewhat seasoned overclockers, will want a stiff drink after trying to absorb this information. So let’s review.
You buy a new 2.66GHz Core i7-920—you just couldn’t splurge on the Core i7-965 Extreme Edition. You’ve got a reasonably chunky air cooler, a good-quality PSU, and you want to overclock that proc. What should you do? First, you need to start goosing up the base clock until you get a clock speed that seems reasonable for the CPU. So, let’s say you want to aim for a nice conservative 3.5GHz. Start by setting your base clock to a speed that will get your CPU in the region. Take it from 133MHz to, say, 160MHz. The target clock speed you’ll want is actually 175MHz for 3.5GHz, but we’ll start with 160MHz.
We’ve read posts on the Internet of some people being able to reach a high clock speed without the need for additional voltage to the CPU, so you’ll want to see if your CPU is capable of it. If you want a good real-world test, run your favorite multithreaded encoder, such as HandBrake. Nero’s Recode is also multithreaded and will put a reasonable load on the CPU. If you want to really torture it, download Prime95 from www.mersenne.org. Unzip it and run Prime95.exe. Select In-place FFTs and make sure the number of threads is set to eight. By default, it should be eight for a Core i7. If it runs for, say, half an hour, you can aim higher. Add 5MHz to your overclock and try again. Go until it fails.
Extreme Edition CPUs feature unlocked QPI and memory ratios and even let you override the individual Turbo Mode settings and change how the CPU throttles under power loads to either let you run higher overclocks or nuke your CPU faster.
Now it’s time to add voltage. A good starting point is 1.35 or 1.375 volts. Since 1.375 is the maximum allowable voltage under spec, you’re actually still playing it very safe. While you’re there, you may want to add voltage to the QPI. So nudge it up from 1.1 volts to 1.3 volts. Some say that the QPI voltage should at least equal the core voltage, but that’s up to you. You should also add voltage to the RAM to get it to spec. If you’re using RAM rated for higher speeds, give the RAM the amount the maker suggests. The safe limit seems to be 1.66 volts.
Intel says it locked the QPI and memory multipliers on its budget chips but some motherboards appear to circumvent this. If your board does this or you’re running an Extreme Edition, which has unlocked QPI and memory multipliers, you can try backing down your uncore and RAM multiplier. Most BIOSes should correct the ratios for you, but remember that the uncore multiplier should be twice that of the RAM. So if the RAM multiplier is set to 10, set the uncore multiplier to 20. If you back the RAM multiplier down to six, you can set your uncore multiplier to 12.
Now reboot and rerun your stress tests. Keep repeating the steps we’ve outlined until you hit your target or hit a wall. Once you’re at your target, do a longer stress test with Prime95 to see if it is truly stable. You may have to add cooling or voltage to get it to run for several hours.
Remember, cooling and quality power matter. If you think you can do all this with a cheap power supply and straw heatsink, think again. Want to know how far can you get Intel’s cheapest Core i7 to overclock with air cooling? Read our case study to find out.
Comments are closed on this article
JCCIII
November 03, 2009 at 8:14am
"If your machine will withstand a couple of hours of Prime95, you’re doing good. If it’ll run over night, it’s bullet resistant. If it’ll run overnight in the middle of the summer, in an 80 degree room, well, you really have something to brag about."
Is not that the truth!
How many times have I wondered if my EE was one the verge of a meltdown this summer?
Wholesalers
September 21, 2010 at 12:04am
Yeah! you are right this is exactly what actually happen cool stuff man I like it ;-)
Regards its David from http://www.wholesalepages.co.uk
sinister213
October 06, 2009 at 10:49pm
I recently purchased a dell studio xps 435t with the i7 processor (920) and12 of ddr3 at a major discount through my school. I plan on making it into a capable gaming system with a few upgrades. Efforts to overclock have been futile. Apparently Dell bios negate the ability to change system settings like clock speed. I opened the towere and there is no lead to what type of board dell supplied me with other than 0X501H. Today i bought an evga classified x58 w/triple sli and a corsair 1000 watt power supply (still waiting for gt300).
However, the salesman at comp usa was bashing the evga board and pushing the p6t. Is the p6t the better board and what are the downfalls if any on the classified board? how capable are they in terms of overclocking? Which board will offer better support for a dx11 gpu? I plan to have all mods done by a local company. they have asus signs everywhere so i know their opinion will be biased. any unbiased input would be greatly appreciated. thanks
MasterShake
September 03, 2009 at 4:55am
I am overclocking my i7 920, and am running Everest to measure the CPU temps. Which temp should I be looking at? I get a status of each core and the overall CPU.
The cores run at about 70 degrees, while the CPU itself shows about 60 degrees.
Thanks!
ghot
August 26, 2009 at 10:37am
Yes, I'm an AMD fan...whats your point? I just got an AMD 955BE to 3.7ghz in 5mins on air...and I haven't even dug into the BIOS, really. Low voltages stock RAM timings...and yes 24 hour Prime95/Blend stable IN an 80 degree room with max load temps at 40-41C. Gimme a month and it'll be at or near 4Ghz on air and 24/7 Prime stable. Yes I do build budget systems...is there something wrong with that?
My earlier comment was just to point out that AMD came up with the architechture, Intel just copied it, threw wads of money at it, and other than ungodly memory benchmarks...it doesn't do much better than an AMD, yet costs alot more.
I could buy Gucci jeans too, but what's the point? Levi's do the same job for a lot less.
I'm really kinda of sick and tired of Intel FAN BOIs and all their BS..to be honest. AMD with their 3 Fabs smacked down Intel badly a few years ago...and they will do it again...why....because they are better than Intel at designing CPU's.
Be my guest Woofa...keep buying Intels...I'll stick with AMD and a vacation instead ;)
Only dead fish....."go with the flow" :/
Take an OS, and edit out all the efficiency, and what you have left is a post-XP Microsoft operating system :)
marscay
October 21, 2009 at 11:56pm
Congratulations, another blind AMD fanatic talking absolute BS.
You need a month to get 4ghz stable 24/7??? I was at 3.9ghz 24/7 stable on a Q6600 2 years ago......yes well done AMD and their followers, a truly amazing feat. AMD were well in the lead a few years back but apart from budget rigs they just cannot compete right now.
Anyone who uses their pc for more than reading blogs is nuts to consider PhenomII over i7/i5, for rendering/encoding duties an i7-920 which only costs another £60 verus the top Phenom II chip (where are you vacationing with that saving, basingstoke for 1 day?) absolutely destroys it.
The only reason you're sick and tired on Intel fan boys is because you know it to be true and you're backing the losing horse to save a bag of peanuts.
pianoman6954
October 10, 2009 at 4:33pm
Intel's entire wafer process is different than AMD's. The QPI is multidirectional and modular without special implementation or seperate chipset intervention, making it nearly infinitely scalable. So its a little hard to believe the architecture is copied. A similar method to handling RAM is far from a complete architecture copy. AMD hasn't been on top since the Pentium 4 was Intels best offering. AMD didn't get it's reputation for being the fastest or the most efficient, they are cheap, that's all.
studlymetts
April 16, 2009 at 2:37pm
i'm going to buy a core i7 920 with 12 GB DDR3 RAM
What other customizations do i need to make my core i7 920 run at 3.2 GHz?
and do I need to buy a better CPU cooling fan after overclocking it to 3.2 GHz?
vfxcorp
April 23, 2009 at 5:55am
Re:studlymetts - Yes, to overclock and to deal with the resultant heat increase you will need two more things: a better thermal paste and a better air cooler than the stock items that come with the Intel processor. Through my own experimentation and web research I have found that OCZ Freeze is the near top best thermal paste and performs 1-2 degrees better than the popular Artic Silver 5 and has a much shorter cure time. A better air cooler can make up to a 10-15 degree difference under load compared to a stock cooler. Based on BenchMarkReviews.com, for a 1366 processor, the Thermalright Ultra-120 Extreme and also Prolimatech Megahalems are the 2009 first quarter bests. Ufortunately Newegg is currently not stocking the Thermalright Ultra-120 Extreme or Prolimatech Megahalems, but I found the Thermalright Ultra-120 at Microcenter.com.
vfxcorp
April 02, 2009 at 3:10pm
Great OC article. I wished they had gone more into the value or lack of value for Hyperthreading being ON or OFF.
I'm overclocking an i7 940 at 176 QPI (4048 Mhz) with some intense Vue 7 renders working up to 72 C. I did notice that by turning off Hyperthreading in the Bios, it saves about 10 degrees! That's a big heat difference. With Hyperthreading ON my Cinebench R10/64 scores are Single 5411, Multiple 21951, and OpenGL 8966. With Hypertheading OFF the Cinebench seems to do a little better on the Single, but does drop a little bit in Multiple: Single 5450, Multiple 19589, and OpenGL 8920.
Would Hyperthreading show more value in video production software I wonder? What software currently takes advantage of Hyperthreading?
Woofa
April 13, 2009 at 6:09pm
If not then it's of no use to you, at least speaking strictly i7. If you do then simply go to intel.com and figure it out, it's not that hard as you'll find it where you find the other downloads for the DX58SO.
Pball1224
March 16, 2009 at 10:30am
With turbo mode still turned on, the best speed I can reach and be stable at is 3.3ghz with a BCLK of 160mhz. Any faster and the temp gets too high and the sys restarts, usualy within 3 minutes of starting a test.
Woofa
February 27, 2009 at 12:54am
I was wondering while reading this why you got such limited results. Not that they were bad, just not noteworthy. Finally there it was, the motherboard you used, "Intel DX58SO “SmackEDover”." I've got nothing against Intel boards, I'm replying from one of my systems that happens to use a Bad Axe 2 with a Q6700 running at 3.6 on air that has been crunching away on distributed computing projects for over a year almost non-stop and zero issues. However their performance "Extreme" boards are not quite up there with many other motherboards when it comes to overclocking and from my experience the DX58SO is not an exception. The Bad Axe 2 I'm using is probably the best of the Intel Extreme category. Actually, strike the probably. I have my hands on a lot of hardware since I build systems and the Bad Axe 2 is the only one of the extreme boards that has been able to get in the same OC ballpark as a number of other makers like Asus, EVGA, Gigabyte and others from the same generation. It's old hardware now and there are other boards I could put this Q6700 in now that would perform better but it's been established so I leave it as there is no sense fooling with this unless the board takes a dive. I built a new i7 920, EVGA X58 on air for myself two months ago and it wasn't even breathing hard at the 3.66 you recorded and there are plenty of other examples like this out there using EVGA X58, Asus P6T, Gigabyte, etc. mbs. Those aren't just bragging number either as they are well documented and I won't even talk about what my 920 is clocked at right now. I have to wonder why you chose this comparison using the DX58SO. Maybe because Intel supplied the whole kit? I don't know. Anyway put that 920 in a P6T or EVGA X58 and you'll get a different OC experience.
As for the AMD fanboy ghot and the ridiculous comments. There's nothing much more entertaining than someone who doesn't have that much knowledge spouting off about the brand they blindly follow. I don't build just Intel systems nor do I blindly follow either cpumaker, in fact for a few years my systems were mainly AMD based. That situation may return someday, but right now if you aren't budget building Intel is the choice. I use and recommend AMD cpus for media centers and they work excellent for that purpose, workstation environs or top gaming machines they aren't the top dog and haven't been for awhile. ANY Core i7 absolutely crushes any other choice out there right now.
macumber
February 08, 2009 at 4:39am
Gordon, are you testing any water cooling, peltier, or other solutions with Core i7? I am one income tax return away from building a system and debating air vs water vs something else. Looked at CoolIt, Thermaltake Bigwater, and Danger Den DIY ... dunno what to do. Was planning on doing some overclocking of a Core i7 920 chip.
Badger1
February 07, 2009 at 5:49pm
Nov. 17 I order my Gigabyte GA-EX58 Extreme mobo, Intel 965EE, a kit of 6 gigs of Patriot Viper EE DDR3 1333mhz and a couple of 150gb VelociRaptors. It all comes in by the 21st, I build it, boot it up and it's unlike anything I have ever used. WOW. I run it for a month and start pushing it. It goes to 3.86mhz with the memory running at 1500mhz like nothing and is still under 40c with air. Everytme I get to 4 ghz I lose stability. I see Patriot says the memory is for 1.65v. I am aware of the dreaded 1.65v + on this CPU but I take it to 1.64 and get 4 ghz stable. It goes into standby mode and locks up. I try different and it seems good until it sleeps for 4 hours and blows my HIS 4870 Ice-Q video card. I put an old X1600 I had it and I'm back up and smoking. I think maybe a bad video card. After another 4 hour slep it blows the X1600. It boots up with a real bad looking screen. I next day a Sapphire 4870, install it and it boos up once, says my BIOS is corrupt and it's restoring. That was the last of that system. Gigabyte said power supply. I tried 3 different ones, new memory, a fourth video card, another mobo and another CPU. I went and got an ASUS P6T Deluxe/PalmOC and i booted right up with my old CPU. Being w/o my system for 16 days, the shipping and return charges I paid made this a sad story. My ASUS was flying so I asked their tech support about sleep mode with my memory set at 1.64v. They said there should be no problem. I put it to sleep for 5 minutes and it mimicked the first system and scared me stiff! I have contacted them 4 times and can't get anything of use from them.
I am now running my memory at 1.5v, CPU on auto 1.325v, BLCK at 150 which gives m3 1501mhz on te memory an sets the CPU at 3.75 ghz. It is going in/out of sleep perfectly and feels like it's running the best I've had.
ghot
February 06, 2009 at 10:28pm
You all know the old story about two disparate people from differnet walks of life ...siwthing jobs or lives for a day etc? I'd really like to see what AMD could do with Intels fabs, for a day, and visa versa. I still can't figure out why Intel just didn't name the processor K11 lol. The "I" in I7 makes it almost sounds like Intel came up with the architecture. Yes, that WAS sarcasm.
Take efficiency, and edit out all the intelligence and what you have left is a post-XP Microsoft operating system :)
Silentblaze513
February 11, 2009 at 4:50am
This is about the Intel i7, not the "budget" amd. The only thing AMD has to stand on is its so called "6GHz" headroom; of course you won't be hitting anything near that unless you have liquid-nitrogen and liquid-Helium. Even if you did hit 6GHz on an amd, an intel at 4 to 4.5GHz (on fucking water-cooling) would kick its ass.
pppriot
February 07, 2009 at 8:19am
LOL. i wonder why AMD can't make something better than the i7 and actually market it. rookie.
canbbb
February 05, 2009 at 9:38am
Sorry MPC, but I followed HardOCP's method this time for overclocking my 920. And it's MUCH simpler:
[1] I simply overclocked my BCLK to 180, for a 3.6 Ghz machine; and
[2] I selected 1523 Mhz for the RAM (I know, weird choice)
Everything else I left at "AUTO". That's it ! Used Prime95 for 2 hours. Stable as a rock. Did not even need to change the voltages.
I'm not one to shy away from the complexities if that would be the only way to overclock the beast, but it's simply not necessary in this case, so why do it so complicated ??
The Rig:
Core i7 920, overclocked to 3.6 Ghz
6Gb Corsair 1600 Mhz DDR3
Swiftech H20 water cooling kit (I know, I could push my CPU even further with this)
Asus P6T Deluxe mobo
and lots of other stuff :-)
Cache
February 05, 2009 at 10:41am
Ugh--that is sloppy and utterly irresponsible. First of all, 'auto' almost always means extra volts--unnecessary volts--and that means heat that was generated for no reason. It's potentially dangerous if you don't have the faintest clue how much power is being used by the components of your system.
I won't disagree that it may be 'easier', but it's far from a good, reliable solution. As a 'first pass' if you want to see if something is possible, maybe--but if you really want to earn any OC chops you have to know how to actually tweak things so you get the best results for a given chip/motherboard/RAM combo. I can look at my Q6600 and recite by memory what all the settings are and I know--I KNOW--that everything is in place as good as I can get with the settings I've set.
Using the 'auto' means that all you did was take a guess and hope for the best, without any real idea what you could have done with your system.
canbbb
February 05, 2009 at 2:16pm
Cache is right. :-)
Really, understanding the components, how it all works, and making sure you're doing the right thing is all important. I have to admit my first post sounded like anyone could do just this.
In my defense, the P6T does a very good job of balancing things out - better than other mobos I've had before. And it's only after reviewing at length the videos on HardOCP's site that I went that route for my last overclock. 'Sloppy' and 'irresponsible' are certainly not the right terms to be used here (but go ahead... flame away if you feel like it).
For the record, my voltages currently are: CPU: 1.275, RAM: 1.5 and QPI: 1.2125... well below what this article proposes, and giving me a very stable 3.6 Ghz machine. Yep, the P6T does deserve that good overclocking reputation it has...
Cache
February 05, 2009 at 7:31pm
Also, I want to apologize for sounding snappish earlier--it was not my intent. That said, I'm running an Asus p5q pro and have had other Asus boards in the past--they really do make OC'ing fairly effortless for people who may not know everything they 'should' do. As it stands now, I've undervolted my Q6600 because I'm really not going too far with it, and I see no reason to throw extra electrons around in there.
And yeah, I left a couple things on Auto when I got around to balancing everything out, it made it very easy to work on one thing at a time and know that if the OC froze up exactly which voltage did it. I think Auto has it's place--it's just not meant to be used as a crutch, if that makes any sense. Also--nice work there!
Cache
February 05, 2009 at 5:00pm
"Cache is right."
Could you relay that to my wife? She's under the mistaken impression that I'm rarely right... ;)
Marcus_Soperus
February 05, 2009 at 8:46am
...this should be required reading for any overclockers and bench techs dealing with the Core i7 procs. The BIOS changes are the biggest I've ever seen. Thanks for posting this!
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