I am trying to bump up my E8400, from what Ive read its supposed to be easy to overclock but I am not having any luck... I get stuck at 3.5Ghz when I try to bump the FSB to 400x9 for 3.6Ghz then OSX will no longer boot, says waiting for root device until I back it down.. I was hoping to get 4Ghz (445x9)

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I have a Sunbeam Core Contact cooler with a Sythe Ultra Kaze 3000RPM fan (133CFM) blowing on it so I know heat is not an issue.. the temps didnt change from 3.0Ghz to 3.5Ghz (idle at 29c)

I also have g.skill 1000Mhz memory, at 3.6Ghz I am running at 960Mhz so I am not even meeting the spec speeds.. Ive even lowered the multiplier for memory and severely underclocked it w/no luck.. running 5-5-5-15 as spec'd and laxing them more didnt help (can get 4-4-4-12 @ 800Mhz which is equivlant).

I have tried locking the PCIE bus to 100Mhz, no diffrence..

I am currently using the AUTO overclocking w/3.5Ghz, VCORE is at 1.24 and its rock solid.. Ive changed it to manual, increased the voltage to the memory to 2.2v, set the vcore as high as 1.40, +.1v to the FSB and tried almost everything to get it to boot 3.6Ghz yet it still hangs loading OSX....

Is there anything I need to tweak on the OS side? I am almost ready to try to see if I can boot an ubuntu cd and run mprime and see if its something wrong w/OSX.. Ive found numerous posts of people reaching 3.6Ghz w/no problems and stock heatsinks in the Windows world.. and most of the people were eventully able to break well beyond 4Ghz w/a decent cooler.

at 3Ghz leopard thought I had a 4Ghz CPU, think that could be a problem?

I am running my E8400 at 4ghz at slightly over stock voltages, but below the max on paper from Intel.. (Whatever that's worth)

You might want to look into forums that are more geared towards overclocking and the like. If you want to go 25% above it's rated speed, you'll need to take the time to get it stable in windows by stress testing, and once you're set, then move back over to OSX. There isn't alot of overclocking in the mac world and so there aren't many utilities to help you out.

Here's a good place to start to see what others were doing with their CPUs to get these speeds:
http://www.ocforums.com/showthread.php?t=544848

And a general guide on overclocking the core 2 duo series of CPUs:
http://www.hardforum.com/showthread.php?t=1198647

There's quite a bit of tweaking and patience required to get up to the 4ghz level with low voltages, but it can be done! Hint.... Boost your VID a little and see where you get, and make SMALL changes to the CPUREF values.

thanks for the tips, I tried them but they got me nowhere...

I did notice this little oddity, with the BIOS configured for 3.5Ghz I manage to get an xbench on cpu test ~240 and CPU-X shows it as 3.5Ghz

However I bumped it from 389 to 395 FSB in the bios which put me at 3.55Ghz... good news is OSX booted, bad news is CPU-X read it as 2.33Ghz (x6 multiplier instead of x9) and now xbench cpu tests gave me ~160.. WTF!? MSR Tools showed it as 3.56Ghz.. I am starting to think OSX has a problem w/me overclocking.

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I also set it to 3.6Ghz and ran memtest about 50% though and had no errors... I tried again at 3.8Ghz and I got errors right away. I guess I'll go poke around on some OC forums and see if I can get any advice..

It's just stepping down during periods of idle usage. It will go up if you use the CPU again.

Ive turned off steping and temporary removed my VoodooPower.ktext thats not thei issue.. MSR Tools showed the right speed and confirmed that SpeedStep was not an issue...

and regardless, with VoodooPower enabled I still get an xbench score of ~290 at 3.5Ghz... so that dont explain why everything got slower from 3.5 to 3.55... I know its not just xbench, system booted slower too with that extra 50Mhz

By me :

Intel E8400 @ 4 Ghz By
1,33 V and
DDR2 800er @ 1168 Mhz By
2,3 V

Stable...

Took a couple of quick pictures of my settings, perhaps they will help you out. I know the screens aren't the same as you have a different motherboard, but you can see the voltages and such I am using. I've been running this setup for about a year now and haven't had any stability issues as of yet.

I've also included screenshots of CPU-X showing my CPU going from idle at 2700mhz to 4050 under load. There's a middle step in there of 3150, but I don't see it too often and it quickly switches to a higher or lower state.

Sometimes you just hit a sweet spot!

Apparently, I guess I'll just have to be happy with 3.5Ghz..

Thanks for the screenshots, Ive set it up identical to that.. even with higher voltages.. I dont have any chipset voltage control though, perhaps thats holding me back

Could be your memory holding you back, my memory is not very fast and I keep it at 900 because of that.

Also, all the chips are different, I actually started with an E8400 that would not go beyond about 3.7 without serious extra voltage. That one was returned because of a "temp bug" and this new one was a really good chip... Luck of the draw sometimes..

I got the same mobo and same proc... I can over clock to 4ghz fine will boot and all just get the waiting for root device problem. the highest I can go without getting the waiting for root device issue is 399x9 giving me 3.59ghz.... Granted Im okay with it... Just I see people OC'd to 4ghz with this processor... Is it the mobo G31M-ES2L??? I mean I'm so lost... I'm temped to oc to the 4ghz mark and load vista, which I know will boot and load.. Why is OSX doing this waiting for root device when attempting to oc past 3.59 or 399x9??

Well I was able to load vista just fine with my overclocked settings... So what could be causing OSX to do the waiting for root device when overclocked to 4ghz??? Now I am completely stumped

I have the same board, different C2Q CPU (Q9550) but having the same problem when trying to go beyond 399 MHzx8.5 in BIOS. I can go 450 MHz+ and the machine will boot Windows just fine and stable, however I get the Waiting for Root Device and "no entry" symbol when trying to boot off of my OS X HD at anything higher than 399 MHz. So, I installed a $12 Silicon Image 3132-based x1 PCIe SATA controller and OS X drivers and voila! Machine boots perfectly at 450 MHzx8.5 into OS X. Onboard PATA controller works perfectly at overclocked speed, BTW. I would guess that it's some kind of OS X-specific ATA driver issue since SATA works perfectly with an add-on card (seen as SCSI) but not with onboard when clocked above 399 MHz. Funny that PATA works perfectly though (my Pioneer DVD-RW). Would love someone to solve this.

anybody have a EP35-DS3L or similar...???
I haven't been able to get past 3.6
with 8500 ram

I have the same problem as well (although with a Q9400); everything is stable in Windows XP (as tested with OCCT); only lower OCs will get Mac OS X back up and running. I would assume the SATA controller is indeed unhappy somehow, if swapping another SATA controller fixed it for someone else.