Overclocking Core 2 Quad Q8400

Hello guys , i am getting a Core2 Quad Q8400 @ 2.66 ghz with 4mb cache , 775 socket . I am wondering how much can i overclock it without touching voltage , and after all i want it to be safe? I got a solid cooler with new thermal paste .

Hi. Tell us about the rest of your system. What motherboard, RAM and power supply are you using?

Usually finding your max on stock voltage is trial and error. You increase the FSB, test for stability, repeat. Once you get instability, drop it back to the last stable setting.

Motherboard gigabyte g41m es2l , ram 2x 2gb ddr2 800 mhz , Nvidia geforce gt740 2gb gddr5 , 450W power supply , 500gb western digital hd,and thanks for ur fast reply mate

I did a little searching and it seems that motherboard isn't a great overclocker with quad core CPUs. Be sure to start off by lowering your memory from DDR 800 to DDR 667.

I've got a overclocked pentium e5300 from 2.6 ghz to 3.2 without touching anything , voltage or ram frequency , so u mean when i OC the new one ill just have to put lower ram frequency ?

There's a big difference in stock FSB speeds between the two CPUs. The E5300 has a 200MHz FSB and it was about 245MHz overclocked to 3.2GHz.

The Q8400 has a 333MHz FSB, so if you are able to overclock to 3.2GHz the new FSB would be 400MHz. That's the base frequency of DDR2-800.

If you don't lower the memory frequency (at least to start with) you'll be overclocking the CPU and the memory. When you get instability you won't know if it's the CPU or memory causing the problem. Underclocking the memory will help you find the maximum CPU overclock.

Oh so ill first put ram to lower frequency then start increasing FSB by a little till the instability issues , thank u for taking time to reply to my questions mate , all best

Cool, keep us updated on your progress.

Hey bro i am here again , and gotta ask u smth once again. I've tried with oc'ing from 333Bus speed to 350 , failed , system didnt boot . i lowered it from 350 to 340 , now it booted successfuly but before i try something else i wanna ask u wheres the problem ? heres the screenshot of current settings http://prntscr.com/5eylbg

Can you post screen shots of the memory and SPD tabs too?

I read somewhere that this board can have a 340 MHz wall, but others said they got past 340MHz no problem (but that may have been dual-core instead of quad-core). Can you look at the motherboard and find the Revision? It seems there are about 4 versions of this board. That might help find a solution to get you farther - or confirm you've hit a wall.

I cant post screen shot of memory and SPD cuz i am not able to shut down system and go into bios right now ( downloading smth ) so ill do it later , for now i can tell u my MOBO is rev 1.0 , and if i've hit a wall theres nothing more i can do ?

Hi Vukasin,
Before messing with the FSB, make sure to set the PCIe frequency to 100Mhz solid. If you leave it to Auto it tends to go up along with the increased FSB.

About figuring out where the problem lies:
1. Did you try different straps / latches for the memory or just left the setting to auto? Sometimes a different latch could work better than the one AUTO selects...Also, try loosening the timings a bit to see if the memory is the issue.
2. Do you have a DRAM Performance Level setting in the BIOS? If so, try setting it to Standard
3. Do you have an option to mess with advanced timings for the MCH? Like MCH clock skew?
4. What's the BIOS version you have? Have you upgraded to the latest BIOS for your motherboard?

Another thing to do to see why the board can't handle the overclock is to try pulling out one of the memory DIMMs. I've had similar issues with 2 DIMMs set up in dual channel on my board. Single channel overclocked like a charm, but I had to go through a lot of trial and error to find a way to stabilize the system with a dual channel setup.

PS.:You can use CPU-Z to give us a shot of your memory/cpu/mobo specs

Oh so , ill try this : remove one stick of ram , putting ram to lower frequency , i think its smth like 2.66 or smth and it will be at 667 mhz instead of 800 , i got a dram performance level and its set to standard or auto , smth like dat , ill try with setting PCIe frequency to 100 , and i got latest bios cuz i've updated it about 2 months ago when i needed to oc my old cpu , so gimme a sec to try it and ill be b soon. Heres the screenshots of cpu-z http://prntscr.com/5ffev3 , http://prntscr.com/5fff0f

yo , tried it , removed one stick of ram , put it to lower frequency , set to 100 mhz PCIe , updated bios once again , tried with 341 FSB , didnt boot , set it to 340 back again and it booted so i think that 340 is just the wall

Hey guys i'm here again so , i did a little more search and discovering capabilities of my pc , and figured out. I've put my PCIe frequency to 105 mhz and changed the FSB to 360 , worked like a charm . Its stable , and btw figured out my voltage was quite high so i decreased it from 1.275 to 1.072 . And by the way i wanted to ask yo , am i able to damage something by changing pcie freq? All my temperatures are good , nothing is more than 60 C.

Hey, that's great! Glad to see you found a trick to get past the 340 wall. It's also good to be able to lower your vcore because that will keep the CPU cores cooler.

You can corrupt your hard drive's data if you set the PCIe frequency too high, but 105 is fine. I wouldn't go over 109 at most.