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Overclocking

The overclocking potential of the Kentsfield is limited by two main factors:

• Two dual core dies in one package means increased bus loading and capacitance; which means that we cannot expect to see FSB speeds as high as we have become accustomed to with the E6xxx series of Core 2 Duo processors
• Two cores also generate more heat than one core, therefore good cooling is even more important than for the Core 2 Duo.

Intel has a nice X-ray style image that shows an illustration of the two dies within the same package - illustrating how the Kentsfield works.

As an "Extreme Edition" processor, the multiplier is unlocked both up and down... so I took the opportunity to test the increased multiplier based overclocking limits of the QX6700 on the original "BadAxe" Intel motherboard that was shipped to us for the review with the processor.

For FSB based overclocking, I moved the processor into our Asus P5D WH, which is our current in-house overclocking champion. It did not dissapoint us, and we got some excellent results, as you could see in our charts.

As always, there were four parts to the successful overclock:

1. Figuring out the fastest stable memory speed
2. Figuring out the fastest stable memory timing
3. Setting the FSB speed and multiplier
4. Getting the right Vcore

Well, five if you consider using sufficient cooling for the processor.

We already knew how fast our Asus P5W DH could go, and given the capacitance and thermal characteristics of the QX6700 we did nto expect to be able to overclock as far as our current in-house record for Core 2 Duo's (3.64GHz with a Core 2 Duo E6400), and did not expect to match our E6700 record of 3.5GHz.

I was pleasantly surprised to be able to get the QX6700 to be stable at 3.45GHz at a 345MHz FSB with a 10x multiplier - frankly, I did not expect to get much higher than 3.33GHz, but this shows you what a combination of excellent parts can sometimes achieve.

Oh sure, if I'd been willing to risk the processor and go for exotic cooling, I might have been able to go somewhat higher - but frankly, I did not think the risk was worth it.

In order to run at 3.45GHz we:

• used the excellent Asus P5W DH motherboard
• set the Vcore to 1.4125 
• set the DDR2 voltage to 2.3V
• set the DDR2 timing to 5-5-5-15 @ 1035MHz
• and set the DDR2 timing to 4-4-4-12 @ 863MHz and below
• set the processor multiplier to 10
• set the FSB speed to 345MHz
• used the outstanding Noctua heatsink with two 63CFM 12cm fans in a push-pull configuration

Conclusion

Ok, I admit, that was a lot of test results to go through.

But what is my overall opinion?

Kentsfield, the QX6700, is a very interesting product, which will greatly benefit those that use highly multithreaded applications that can make good use of the four cores.

Intel is working hard to promote multi-threading to software houses, and is producing quality tools to identify critical paths and allow for better load balancing. I am skeptical about automatic loop parallelization, as most loops are too fine grained to make effective use of multiple cores given the overhead of launching and retiring threads.

That is a pretty impressive list showing the buildup of companies working on multi-threading their applications, however until the products are on the shelves and ready for purchase, most of the advantages of four cores will not be available to the average user.

For the average home user, it is overkill, but then again, the average home user is not going to spend $1000 on a processor either; so that is not the market it is aimed at.

For gamers, while Kentsfield does not hurt, an X6800 will beat it in most games as the software houses STILL have not significantly multi-threaded their game engines yet. But when they do... watch out!

For media professionals, who need to transcode videos, render animation, encode music and video, the QX6700 is a winner. It can literally almost double the performance of a system for these applications; which, if you are a production house where time is money, can save back the cost of upgrading to Kentsfield lickety-split.

For developers, VT support with four cores means being able to run quite a few virtual machines at high speeds; a capability that will also be most appreciated for server use.

I have not tested it for server use yet, however I suspect it would perform fairly well, but not as well as a two socket dual Opteron solution due simply to FSB vs. Hypertransport and on-chip memory controllers. It would scale very well for applications that are more compute bound than memory bound, so it is still an interesting product. Once Intel goes to a native quad core solution (all four cores on the same die, with out of band cache coherency control) with an integrated memory controller and CSI AMD will have some tough competition to face in the server market; however until then I expect Opterons to dominate.

Mind you, AMD has quite a bit of catching up to do on the home/small business performance part, Core 2 Duo bests the FX62, and Kentsfield won't have any real competition until the K8L arrives - mind you, 4x4 might surprise us as it has far greater memory and I/O bandwidth.

Would I buy a Kentsfield?

If I was making a living with video, audio, or rendering, in a minute.

Otherwise, I'd go with a nice Core 2 Duo, or even an AM2 X2 based system!

• See also the review of Intel's Quad Core Q6600 by our friends at OverclockersClub.com for more Quad Core goodness!