Core i7 920/940 overclocking guide

Core i7 920/940 overclocking guide

Related links:
How to Overclock C2Q-Quads-C2D-Duals

Written by monkey7

Ever since the i7 was first mentioned the rumour machine about overclocking it has been spinning at full speed. The first rumour was that overclocking would be impossible because of the removal of the good old FSB, leaving the overclockers with nothing to increase. After the first rush of panic people started to actually think about what would replace the FSB: base clock (BCLK). Increasing this would increase the overall clock, right? Right. After the lifting of the NDA (and on some dubious sites before) the overclocking results were released. An average core i7 920 (2.66gHz, €300) turned out to be able to overclock nearly a full gHz.

But removal of the FSB and the introduction of the BCLK means a lot more chances. Everything is linked to the BCLK, which has confused quite a lot of the old school overclockers. Just to sort that out and set new overclockers on the right path, I've written this guide to core i7 920 overclocking.

First of all: neither me nor overclock3d is responsible for the damage you might do to your components following this guide.

Step 1: preparation
To overclock properly you should first inform yourself about the risks and advantages of overclocking. I will not be writing this all out, but this is the short version:

Risks:
- Shortened life of components when giving more volts than specified
- Extremely shortened life of components when giving an extreme voltage
- System instability
- You could contract the Megahurtz fever

Disadvantages:
- Additional heat output

Advantages:
- Higher FPS in CPU based games
- More F@H ppd
- Higher benchmark scores

Does overclocking really increase performance?
Yes it does. Just look at the CPU scores below (program used: 3DMark vantage advanced)

At stock:
This image has been resized. Click this bar to view the full image. The original image is sized 984x570.

At 3.7gHz:
This image has been resized. Click this bar to view the full image. The original image is sized 983x569.

With a difference of about 6000 points this would represent a considerable increase in CPU based gaming performance.

Having read this, you should start concentrating on the theory behind core i7 overclocking. The system is pretty easy: you have a base clock (BCLK), to which everything is linked using multipliers. This base clock can be adjusted from 100 to 250 in steps of 1. Stock is 133.

Multipliers
The following multipliers are available:
- CPU. With the 920 this is 12-20x
- QPI link (36, 48, slow). The QPI isn't really important for singlecpu systems, but keep it below 7-8gHz as most seem to be bugging out around that range.
- Memory (6, 8, 10, 12, 14, 16x). Well quite obvious. Make sure your ram is running as fast as possible but don't overdo it.

Voltages
When pushing hardware over its rated specifications it will most likely need more voltage to run properly. The following major voltages are available on the i7:
- vCore. This is the juice going through the actual core. Stock: 1.18 Max. safe: 1.35 Max. extreme: somewhere around 1.55
- VTT (asus names it different). This voltage is going through the memory multiplier which is now integrated into the processor unit. Stock: 1.1-1.2 Max. safe: 1.35 Max. extreme: somewhere around 1.55
- vDIMM is going through the memory. Stock: 1.5-1.65 Max safe: 1.65 Max extreme: 1.5*VTT or VTT+0.7

Energy savings
As all experienced clockers know, Intel has some features built into their CPU's that lets them use less power when idling. Overclockers however, are not interested in that power consumption at all and those features go at the cost of stability.

The following features are recommended to be turned off:
- C1E state
- SpeedStep

HyperThreading
Revived from the old P4 days is hyperThreading (HT). HT basically means that a core is pretending to be two cores. In the i7 series Intel decided to have the cpu act like an octo core while being quad. This feature could be very useful in truely multithreaded applications but seems to make the cpu require 0.05 additional vCore. As long as you are not an extreme clocker or single/dualthreaded applications (games) user I'd recommend keeping it on. Personally I have it turned off for my F@H SMP client.

To be continued

Core i7 920 overclocking guide - Overclock3D Forums


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Intel's Core i7 Extreme Edition 965 overclocked to 5.5GHz



CPU-Z Validator 3.0

Intel's Core i7 Extreme Edition 965 overclocked to 5.5GHz

I have hte 965 now - it is just a matter of time to find quality components and save up the money for them - Still agonizing over the monetary crunch, but hopefully I'll get to take mine to some nice OCs....

I have the 920, I blink and it moves. What would you possibly need more than 4 GHz at the current point in time? I can already max out crysis.

corei7 said:

Thanks for posting this, How far can you overclock 920?

With extreme cooling (phase change, liquid nitrogen) I've seen enthusiast benchmarks reaching well over 5.0GHz+.
Prime example of 5.5GHz i7 OC.
The OP in that thread is using the D0 stepping i7 so it runs cooler than the original C0 stepping 920's.

I just finished my initial 920 OC attempts, and wanted to see how far I could take it with just a real good fan cooler and no messing with voltages. I want a nice balance between having juice when you need it to being somewhat green.

I only adjusted the ratio, BCLK, DRAM Freq, and 5 of the DRAM timing parameters. I ended up with 3.82GHz and DDR3-1450 7-7-7-20. The QPI is around 3400. I can run with all 8 VCPUs at 100% for two hours without problems. My system wattage goes fron 294 idle to 495 at 100% .

Edit: New OC: 3.94GHz: manual@ 21 CPU Ratio/ 187 BCLK / 3177 UCLK / DDR-1499 / 7-7-7-22 / 1.25625v CPU / 1.31250v QPI-DRAM / 1.64v DRAM / Others Auto
Edit - lowered my CPU voltage to 1.2625

DJ