Windows 7 - C2Q Q6600 or Q8400?

OK...so right now I am currently running the Core 2 Quad Q8400 at 2.66Ghz. In a machine that I have in the closet, I have a Q6600 @ 2.4Ghz. I know that I can OC the 6600 to a little over 3 Ghz on stock cooling, no problem. I tried to OC the 8400 up to 3 the other day and got a bios error about a 333Mhz processor being installed and then forced to reboot back into the bios.

My question is: Should I throw the 6600 back in here, or should I stick with the 8400? The question is in terms of which I would get the best performance out of.

My mobo and other specs are listed below.

I wonder if the difference is the chip itself or the motherboard, but I have a Q8400 in a Gigabyte EP45-UD3P and it OCs like a champ. I can hit 3Ghz with decent temps (with a Freezer Pro 7) and have had one blue screen trying to push it up to 3.5Ghz. Every PCU is different but i love the Q8400. (I like my i7860 more haha) but I think the Q8400 is a great CPU. I think it's the board or CPU (or cooling) if you're having problems getting a stable 3.0

All that said, the 6600 is one of the best for a good reason, but performance would go to the Q8400 all things equal I believe.

Thanks for the reply nate. Yeah, I'm guessing it probably is the mobo, as that was the first time I had attempted to OC since building this new rig. I'm thinking I will stick with the 8400, and just see if I can find some settings in the bios that will allow me to OC it a bit.

I do like the Q8400....you already know this I'm sure but you might see if there's a BIOS update for the board. Sometimes they add OCing features. You could always spend $120 and get a EP45-UD3P too. I have never loved a board as much as this one.

All the best.

Performance might be tricky to figure out here. As you can see in this chart, Intel® Core™2 Quad Processor - Specifications

The Q6600 has 8MB of L2 cache...while the Q8400 only has 4MB of L2 cache.

The Q8400 runs on a 1333Mhz FSB, so a 333Mhz bus quad pumped
The Q6600 runs on a 1066Mhz FSB, so a 267Mhz bus quad pumped

So, it all depends on which you take more advantage of...the additional L2 cache or the faster bus and memory speeds possible.

When I did my build, I went with the Q9550 to get the 12MB of L2 cache and the 1333Mhz FSB. And I have been quite happy with that CPU. On my GA-EP45-UD3R 1.1 rev mobo, I'm running that 2.83ghz at 3.20 on the stock air cooler with no heat issues at all.

Well, I updated the bios, bumped up the voltages a notch, and have it set on 2.8 for now. Gonna check the temps in a bit and then see about reaching 3.0.

Weird thing was, updating the bios seemed to wipe almost all of the drivers from my sytem.

Edit: Nope...seems like 2.8 is as far as I can push it.

You can only push it from 2.6 to 2.8? There must be something wrong, you should be able to get it to 3GHz and over.

I think the problem may be that I haven't bumped the processor voltage any. Anywhere between 2.85 and 3 and it would blue screen right away.

Think I could get it higher if I boosted the processor voltage?

You also must remember 45nm CPUs react differently from 65nm (like the Q6600) to OCing

The 45nm CPUs (like the Q8400) are a little different to OC. If you usee the exact same methods as 65nm CPUs you will not get the best results.

Read up on OCing the 45nm chips. I find them easy to OC but they are not the same as 65nm.

Yes, and the 45nm CPUs like a small bump in CPU termination voltage to (not sure if that option is on your board) I had a lot more luck when I bumped that a bit.

Also, I know people will have mixed reactions to this but I have found this to be a pretty good "general" guide on how well CPUs perform. They have good lists on cards and hard drives too.

http://www.cpubenchmark.net/high_end_cpus.html