I have a E8400 running on a Gigabyte P35-DS3L. I've achieved an overclock to 3.4Ghz. I'm really trying to get upto 3.6. At 3.4, I can run Orthos fine. At 3.6 hour, it crashes within 5 seconds. Windows Vista starts up, but even Vista crashed.

My temperatures seem to be fine, around 40C for the CPU according to the BIOS and Gigabyte's utility in Windows. What could be holding back the overclock? I've tried doing some research and people claim you can get upto 3.6 easily without messing with voltages. I'm thinking my memory is holding me back. I think currently it's running at 756 or something up from the 667 (ddr2) stock. I really don't want to spend $50 -60 on new ddr2 800 memory if it won't do me any good.

I wouldn't trust the bios readings. Grab Coretemps and find out your idle temps and load temps before doing any more OCing.

Also, list your settings.

One way to get a rough idea of RAM vs CPU issues is to run Orthos in both "small FFT" mode and "blend" mode. Small FFT mode stresses mostly the CPU, while blend stresses both CPU and RAM. If you get errors in blend mode and not in small FFT mode, you're likely dealing with memory issues. Certainly OCing your RAM could lead to instability.

@Evilonigiri

Which settings? Everything is set to auto. This is a P35-DS3L from gigabyte if that helps any. FSB has been increased to 378 I believe to get to 3.4GHz. RAM timings are auto too. They are at 5-5-5-18. One guy told me those timings were horrible, but from my research on the internet, it seems tighter timings and such would not really increase game performance by more than a couple frames per second, so I haven't been too worried about messing with those.

Mondoman... I tried overclocking by increasing the FSB again, and this time Windows would not load at 400FSB on my e8400. Had to go back to 378 (3.4GHz) to get it to run stable.

You'll need DDR2-800 to get 3.6Ghz or greater. the 667 just isn't overclocking well enough for you. And leaving stuff on Auto is not what I would recommend doing for overclocking. Also, auto often undervolts your memory. Find out it's recommended voltage and set it manually.

Try increasing your NB voltages. It's very possible your ram just can't handle it.

I believe the DS3L has a little bit of ceiling at 400FSB. I ran into a problem when trying to run my E2180 @ 3.2 by doing 400x8. It would load into Windows but Prime would lock it up. Yet when I did 320x10 I was able to run prime for 6 hours. By this testing would this say the problem could be a FSB ceiling on the DS3L?

Did you increase the MCH and fsb voltage? Nearly all P35 can do 400Mhz fsb.

I did try setting the FSB MCH to both +0.2 and it crashed just as readily when on defaults, I'm not sure but assuming since it runs fine at 10x320 that it is the mobo...I do have a revision 1.0 board, maybe thats why it crashed?

Updating the bios to the latest version could help.

Most likely it's the CPU itself that can't OC. I've been hearing people having difficulties going past ~3.2GHz, and in order to acheive 3.4GHz requires massive vcore.

If you want, set the VID to 1.5V and try again.

@OP: Read P35-DS3L OCing HOW TO

I tried setting 1.5375V in BIOS which gives me 1.504 IDLE in windows and 1.474V under load. When I did the 6 hour pass on prime(10x320) I had BIOS voltage set to 1.525V. With 1.5375V the 8x400 settings locks my system less than a second from the time I click the test button. This does bring some concern as I eventually plan to maybe get a E8400/Q6600 when there cheaper, but those chips require a high FSB around 400 do get the sweet spots....hopefully it is just the chip...

If you're having issues at 8X400 yet you're fine at 10x320, obviously it's the ram or motherboard. Setting the fsb to ram ratio to 1:1 and laxing the timings to 5-5-5-15 should help. Also setting the FSB, NB, and SB voltage up one should also help.

Of course it's possible that you've reached a wall, but the Gigabyte should be able to do 450MHz.