Got 3.9 ghz on E8400... what next?


Mar 9, 2009
Hi, all. I'm not a newb to overclocking, but it's been a while... my last OC'd system was a Pentium IV. Let's get down to it

-Gigabyte GA-EP45-DS3L
-4GB OZC PC-8500 DDR2 1066
-E8400, rev E0 (multiplier is 9x)
-Scythe infinity cooler (very good 120mm fan)

Current state of OC

9 x 434 mhz FSB = 3905.6 mhz
BIOS vCore set to 'auto'. CPU-Z reports 1.365 at idle, 1.344 under load

DRAM freq. is 520 mhz using 5:6 divider, 5-5-5-15 @ 2.2v as per OZC instructions.

Everything NB, SB, vCore is set to AUTO. Memory set to 2.2v from 1.8v stock (they won't work any other way).

Prime95 has been running for 2 hours on BLEND with no errors. When I OC to 4 ghz and above, small & large FFT don't crash, although small FFTs generate the most heat.

Now, when I push it to FSB 445 for 4.0 ghz, Vista 64 loads just fine. Prime95 will run anywhere from 10 min - 20 min before encountering round off error. 3.9 looks to be the limit on stock voltage. But when I increase the voltage to 1.39, my idle and load is the same as if I'm on Auto! I don't want to keep pushing past 1.4v just to see if my Vdroop will kick over to the next voltage increment.

So, questions for the experts

1. How far should I push BIOS vCore to get idle/load vCore readings to jump over to the next increment for stability?
2. Should I increase voltage to the NB & SB? I can't identify what they are in my Gigabyte BIOS.
3. Under power settings, do C1E, C2, and C2E affect overclocking?
4. My RAM likes to run at 533 mhz @ 2.2v and not a tick higher. What happens when I keep the voltage at 2.2v but underclock it via divider setting to something like 442 mhz? Usually my RAM will auto-adjust to 5-5-5-13 according to the timing tables when I underclock it. But shouldn't I be lowering the voltage down from 2.2v when I'm not at the full 533mhz?

Oh, and temps are roughly 36c at idle (2600 mhz = 6.0 x 434 FSB) and hit maybe 57c at full 3.9 ghz, occasionally holding 60c.

Ultimately I'd like to go for a stable 4.0 ghz - 4.2 ghz if possible, but I'll stop now if adding 1.4 vcore will shorten CPU life.

THANKS! Much appreciated.




Jan 7, 2009
AL, it would be a good idea to first take all your Bios settings OFF auto. You should set all your Bios settings to there default values at stock speed then slowly increase the FSB making the needed changes to voltage one at a time to gain stability. Yes it's a long, slow process but it's the best way to do it.

OK, that being said, it seems to not work for most people any more, too slow and time consuming.

E8400 (E0) 's are known for being able to OC to 4.0 Ghz with very slight vcore increases. You should NOT need to go above 1.3625. Right now I'm running my E0 at 4.14 Ghz @ 1.280v vcore. You do have to get rid of some of your auto settings, they are only going to hurt your OC.

I would start at:
vcore: 1.3625v
FSB: 430
NB: 1.3-1.4v
vtt: 1.1-1.2v
pll: 1.5v
Memory strap: 2.0 (1:1) to take the ram out of the equation
sb: default voltage
Ref: .59, .63
PCIe: 100
keep ram at manufactures recommended speed and voltage

Slowly works your way up and test, then lower voltages and test then set ram and test.

Good luck