Learning to OC with an i7/P6T


Mar 6, 2009
Hi all,

I'm looking for some guidance WRT overclocking/tweaking my new computer. I am strictly a hardware guy so this is all new learning to me (read= newbie)...

Here is my setup:

Asus P6T Deluxe
Core i7 920 2.66GHz
3X2GB (6GB Total) Corsair DDR3 SDRAM 1333MHz
WD VelociRaptor 300GB 10kRPM SATA2 System Drive
PNY nVidia Quadro FX1700 512MB RAM
Corsair CMPSU-750TX 750W Power Supply, SLI/Crossfire Enabled, Active PFC, Core i7 Compatible
Single Samsung DVD+/-R Drive 22X w/ LightScribe
Cooler Master V8 CPU Cooler
Hiper Anubis ATX Mid Tower Case
2X Noctua 120mm Fans
Vista Ultimate 64Bit
Dell 2408WFP 24" LCD Monitor 1920X1200

Here is a snapshot of CPU-Z:


There are a couple specific things I would like to address:

1) I'd like to make full use of my RAM. I think it is set to only 1066MHz now but I'm guessing based on this article (LINK) that I can change the memory multiplier to get the advertised 1333MHz. Questions: Can I get even more speed? What am I risking/trading-off by doing this?

2) How much of an overclock would be reasonable given air cooling with my CMV8, and how much benefit will I see in daily use/Solidworks(CAD)/light gaming? Can anyone explain exactly what considerations are involved in overclocking in layman's terms, or how all the settings mentioned in articles like the bit-tech OC guide work together to make a functoning computer?

3) What is QPI Speed and what benefit is there to pushing my setup from 4.8GT/s to 5.8 or 6.4GT/s like it says I can in the Maximum PC article?

4) I want a stable system that without a lot of "nannies" doing stuff in the background. I just found out that the intel speedstep is what's causing my processor to run at 2.79GHz rather than the normal 2.66 in my CPU-Z snapshots... Do you guys typically leave this stuff running or streamline the BIOS to keep it as simple as possible.

I'm a quick learner but I need someone to help point me in the right direction.



Feb 3, 2009
I got the i7 920 on the P6T with the same cooler as you. I'm OC'd to 3.8GHz. Check out this video. It shows you how easy it is:


With this OC, and 12GB of memory at 1523Mhz, my CPU temp idles around 40c. I've been running the settings specified in the video a couple of weeks now and it's been rock solid. To summarize, the settings are:

BCLCK frequency 190
Turn off speedstep
DRAM Frequency 1523MHz
CPU Voltage 1.35
DRAM Bus Voltage 1.66 (ignore warning)


Decided to reseat the CPU. Last time when I replaced the old cooler with the V8, I didn't wipe away the previous thermal paste (how bad of me). So, I cleaned it up, applied a nice line of Arctic Silver 5 right across the cores as documented on the AS5 site), and presto. My idle CPU temp dropped into the high 30s.



Mar 6, 2009
Okay, just got home from work and made some tweaks to my BIOS. Most of it was just to make life simpler but I will document it all anyways.

Turned off Full Screen Logo (to see POST)
Turned on Q-Fan set profiles to Standard
Disabled Intel SpeedStep
Set Ai Overclock Tuner to Manual mode
Set DRAM Frequency to DDR3-1333MHz


After that I saved and rebooted. I saw in the POST screen that the memory was indeed showing up as 1333MHz and this is confirmed by CPU-Z. Also, the timings now match the advertised timings per Corsair.




Mar 6, 2009
While poking around on the net, listening to my music and stuff last night I noticed my comp was running 35-40C (CPU & Mobo) versus the 32-35C it was before I made the changes... I wonder if this is simply a product of turning off the speedstep and power saving utilities? Booted up this morning and things had settled down to right around 35. It could also be because I changed the fan-speed profiles... I noticed the chassis fans are going much slower than they were before and the cpu fan is a bit higher.

I also noticed during a reboot into BIOS that my CPU voltage had somehow been set to 1.21xx so I changed it back to auto... This was in between my high and normal temps so perhaps that was forcing my chip to run hotter?

blackened144, I'm trying to learn about QPI so correct me if the following interpretation is wrong:

The QPI (QuickPath Interconnect) is essentially a replacement for the more familiar term FSB (Front Side Bus). The QPI is the link between the i7 920 processor and the X58 Northbridge. The QPI "speed" is the number of transfers per second in one direction. The QPI transfer rate (GT/s) times the channel width equals the total bandwidth of data that can be transferred across one link and in one direction.

I have read that the QPI is a 20 bit wide link. So if you take a 2.5 Byte link (20 bits divided by 8 bits/Byte = 2.5) * 4.8GT/s you get a bandwidth of 12GB/s per direction.

By upping the setting to 6.4GT/s you can increase the bandwidth, the communication between the CPU and Northbridge, up to 16GB/s.

What I'm trying to understand now is any limiting factors on the X58 or i7 side that are a "weak link" in the communication chain. Meaning, can I take advantage of the increased QPI bandwidth with stock CPU speed? I'm also trying to better understand the CPU/RAM interface.

*Edit* Another question: Am I not utilizing my RAM correctly by forcing it into 1333MHz? I've been reading that forcing your RAM speeds higher without tweaking the voltages causes it to go into 2-channel mode making it slower than the lower speed in 3-channel mode. How can I test for this?


Aug 17, 2006
What you are saying about the QPI is correct and your RAM should now be good. On boot, your BIOS shold tell you if you are in tri or dual channel memory mode, and that second CPU-Z screen will tell also you which mode your in. Your screenshots show "triple" right now. Now as i said before you are correct in what you said about upping the QPI to 6.4GT/s, but that will not have any effect on your actual CPU clock speed, just the bandwidth available to it. In order to overclock your system, just like with the older FSB, you just need to raise the QPI bus form its default of 133Mhz. Your clock speed is 2.66Ghz (133x20), if you could get your QPI up to 150 using your multiplier of 20, youre now running at 3Ghz. So basically you just want to slowly raise the QPI bus until the system is no longer stable at stock voltages. This should not have too big an impact on the temps. Once you hit that wall though, you can then up the voltage on the CPU and go even higher. Once your upping the voltage though, the temps will increase much more.


Mar 6, 2009
Would I see any benefit or drawbacks to increasing the QPI transfer rate without overclocking the bus speed (and thus messing with my CPU, QPI and memory speeds)?

Being a mechanical guy I imagine the CPU as a bucket with some water in it and a spigot on the bottom. To get the water out of the bucket you put a hose on the spigot and open it. All else being equal, the water flow out of the bucket is limited by the size of the hose it is flowing through. That hose is what think of the QPI as.

If the QPI rate of 4.8GT/s isn't limiting how quickly the info is getting from the caches to the X58, then I have no interest in messing with it.

However, if I can predetermine a solid, safe bus speed that gives me reasonable memory and QPI speeds with the available multipliers, then I will try that.

The only thing I know is that the QPI speed ("QPI Link" in CPU-Z) should be 2x the memory speed (which I understand to be 2x the "DRAM Frequency" in the memory section)... Maybe that isn't even right.

All I really want is for everything to be running as intended, and then to eliminate any bottlenecks built in to the system to distinguish the 920 from its more expensive i7 brethren.


Mar 6, 2009
Bumped up the "QPI Link Data Rate" to 6.4MT/s when I got home. No noticeable difference in my normal web-browsing, nor does it show up anywhere in CPU-Z.

Man, I really need to get some software on this piece!
1) The i7 920 is already so good that you probably don't need to overclock. Turn on the task manager, and observe how busy each of the cores are.
My guess is that you will be shocked at how little usage there is.
2) I think a very safe overclock is to the level of the fastest variant at stock. That's the i7-965 @3.2
3) I suggest using speedstep, The cpu will downclock when there is little to do, and ramp up to an extra step when pushed. Don't forget that vista will control the minimum and maximum rates in the power settings.
4) The easiest way to overclock is to up the bclk from 133 to 160. That gives you the 3.3 you want. Leave everything else on auto.
5) The integrated memory handler is very good. It has no problem feeding the cpu, regardless of the ram speed or timings. Leave the ram to auto where it will be stable.

Purists and status seeking overclockers will tweak things more, but there is little real difference that shows up in application performance.



Mar 6, 2009
Thanks for the reply geofelt.

Last night while watching some streaming video, full-screen, the computer locked up twice. No mouse movement, no escape, no ctrl+alt+delete... Had to hard reboot each time... The weird thing was I was able to watch several videos with no problem. Temperatures seemed completely normal too...

Here what I had done that may have messed things up:

1) VPN into wifes work and used remote desktop to access her PC. Once in, I tried using solidworks and pro/e without much luck. (graphics issues and very slow)

2) For some reason I thought that if I downloaded the approved drivers from the solidworks site, that may help the performance of the remote desktop. (This was probably silly since I don't think the graphics being provided over VPN/RD are being computed by my machine, rather the machine at the office.

3) I had pushed the QPI Data Link Rate to 6.4MT/s as noted in my last post.

After the first lock-up I changed the QPI data link rate back to auto.

After the second lock-up I changed everything back to the default setting (Ai overclock tuner - auto, speedstep - enabled) except for the RAM setting of 1333MHz.

I then proceeded to watch another video with no problems. It was very weird how intermittent it was, but how similar it was both times... locking up mid-video.

After the videos were done I decided to try to figure out why the hard drive is constantly clicking/whirring even though the computer was completely idle. There are times when I will boot up and the HD will be screaming along for a good two minutes after windows login even if I don't even touch the mouse. I don't have a lot of software installed and no programs in the startup folder... ???

I did some internet searching and the only thing I could gather was that perhaps Windows was indexing during that time so I removed all the folders from the indexing control panel. I haven't noticed if it makes a difference or not.

Another thing I noticed while viewing the resources manager is that my computer is always using, at a minimum, ~1.65GB of RAM. This seems like alot to me... Perhaps it's because I have windows on full Aero mode? Surprising though, either way.
To verify that your overclock and system is stable, do two things:
1) Run memtest86+ for several passes without error.
2) Run prime95 for long enough to heat up the cpu to it's hottest. This will be an hour or so. Use the option to check for rounding errors.
If you get no errors, then your issues will be software or drivers.

Also check that there are no bios updates that might address the issue. Don't take the risk to update the bios unless you think the update might address an issue that you have.

Vista indexing is a good thing. It is done at low priority so it should not interfere with anything you are doing.
The benefit is that searches are almost instant.

Vista keeps things in ram that you have used before, in anticipation that it might reuse them. It might pre-load things if it thinks you might be using them soon, again using low priority i/o. You will see this in the cached physical memory part of task manager. The only permanent part of vista is the non paged kernel ram which will be very small, like <100mb.