Overclocking Escapades: Intel socket LGA775 Core 2 Duo E8400 C0 stepping

[Tech Tweaker]

I thought I would try overclocking an E8400 C0 stepping C2D I had here to see what it could do.

Step 1. Find the lower voltage limit of its stability.

So far I've got it to run at 1.14-1.17V (after Vdrop and Vdroop) and it is Prime95 stable, down from the stock 1.25V. Had it running at this setting for around 5 hours now with no noticeable issues. Temperatures seem to be the same as at the stock voltage, which is odd considering I was expecting at least a little drop in temperature; I did see a slight temperature drop when I did this on one or two of my AMD CPU's as well as my Intel E4400 C2D and figured I would see a similar change here.

Step 2. Seeing how much voltage it takes to run at say 3.5 or 4GHz, or if it will run at those speeds at all.

Step 3. Finding a good 24/7 overclock that is stable and doesn't run too much hotter than stock.

CPU in question has a VID of 1.25V, date code is Q825.

Stock (3GHz 333x9): 1.1v (1.13125v)-EP45-UD3P
3.1GHz: 1.1v (1.13125v)-EP45-UD3P
3.2GHz: 1.12v (1.15v)-EP45-UD3P
3.3GHz: 1.17v (1.18750v)-EP45-UD3P
3.4GHz: 1.18v (1.21250v)-EP45-UD3P
3.5GHz: 1.22-1.23v (1.25v)-EP45-UD3P
3.6GHz: 1.25v (1.2750v)-EP45-UD3P
3.7GHz: 1.296-1.32V (1.35V)-EVGA 780i SLI
3.8GHz: 1.336-1.376v (1.40v)-EVGA 780i SLI
3.9GHz: 1.368-1.408v (1.43750v)-EVGA 780i SLI
4GHz: 1.408-1.448v (1.4675v)*-EVGA 780i SLI

Intel Core 2 Duo E8400 C0 #2 overclock settings
VID: 1.225v
Stock (3GHz 333MHzx9): 1.104v (1.125v)
3.2GHz (356x9): 1.152v (1.175v)-47°C
3.3GHz (367x9): 1.168-1.184v (1.20v)-49°C
3.4GHz (378x9): 1.20v (1.225v)-51°C
3.5GHz (389x9): 1.248v (1.275v)-51°C
3.6GHz (400x9): 1.280v (1.3v)-54°C
3.7GHz (412x9): 1.328v (1.35v)-55°C
3.8GHz (423x9): 1.344v (1.375v)-55°C
3.9GHz (434x9): 1.376v (1.4v)-58°C
4GHz (445x9): 1.392-1.408v (1.425v)-58°C
4.1GHz: Not happening at any settings

 

[Janus67]

What cooler are you using? Maybe you can be at a point where it won't get much better? Are your idle temps any better?

 

[Tech Tweaker]

What cooler are you using? Maybe you can be at a point where it won't get much better? Are your idle temps any better?

I'm using a Thermalright Ultra 120 Extreme. Idle and load temps are the same.

Idling at 38-41°C, load at 48-50°C with Prime95 blend test.

 

[I.M.O.G.]

These don't put out a whole lot of heat, I'd say it could be hard to see a temp difference with a cooler like that.

What mobo you using?

 

[Tech Tweaker]

These don't put out a whole lot of heat, I'd say it could be hard to see a temp difference with a cooler like that.

What mobo you using?

A Gigabyte GA-G33M-DS2R.

 

[Tech Tweaker]

Finally had some time to do a little more testing on this yesterday.

Got it up to 3.6GHz so far, had to set voltage to 1.325V in bios (which ends up being 1.28-1.3V in the OS at idle, and 1.25-1.27V under load with Prime95). VID on this chip is 1.25V by the way, don't think I mentioned that before. Also, I switched the HS over from a TRUE to an Ultima 90, because I figured I'd reserve the TRUE for something with a higher TDP.

Stable with blend test for a 1 hour test.

 

[dyckah]

I had my e8400 sitting at around the 4.5Ghz mark for my 24/7 overclock, and damn did it ever throw off a lot of heat at that kind of clock.
love that chip, super easy to overclock, and super easy to stabilize.
i think mine was a c1 stepping though.

 

[Tech Tweaker]

Well, it was stable for about a week.

Had to reboot my system today and now after it started back up it refuses to boot at any settings higher than the stock 3GHz, won't even run at 3.3GHz, no idea why. Tried increasing voltages, didn't help though. Could have something to do with the fact that my board only supports up to 1333MHz FSB natively, which is odd if that is the reason since I had it running at 1600 for a week without breaking a sweat.

 

[bittbull187]

yea my e8400 on msi p7n @ 4.0 idles around 38-40 load 69-72. beast little chips o i am using xiggy dk s1283 in push pull

 

[Tech Tweaker]

Well, I've got this CPU in for testing again.

Strangely, when I pulled it out of the CPU clamshell holder I was storing it in most of the pads on the bottom had turned a brownish color (corrosion apparently?), it still seems to be in good working order though. Don't know why it did that, I've never even touched the bottom of the CPU.

This time on a board that can actually handle it, using my Gigabyte GA-EP45-UD3P. I'm expecting results to be a LOT better than with my G33M-DS2R.

Idle and load temps seem to be the same as last time. Core 0 is at 37-39°C at idle and Core 1 is at 40-42°C at idle. Core 0 is at 46-48°C under load and Core 1 is at 48-50°C under load with Prime 95 small fft's.

 

[OptyTrooper]

I have one of these as well I'll probably pop in my P5K Pro today or tomorrow.

 

[Woomack]

I wanted to bench one E8400 couple of days ago but it came damaged ... and I haven't noticed that couple of months ago when I got it . It boots but max ratio is x6 and only cache L1 is working.
Lately about 50% hardware that I get is or broken or has other issues. Even if I bench something then is usually degraded so results are pretty bad.

 

[OptyTrooper]

I wanted to bench one E8400 couple of days ago but it came damaged ... and I haven't noticed that couple of months ago when I got it . It boots but max ratio is x6 and only cache L1 is working.
Lately about 50% hardware that I get is or broken or has other issues. Even if I bench something then is usually degraded so results are pretty bad.

I'm dealing with the same thing 2 dead 3770K 1 dead 3570K 1 dead 4670K ans AsRock Z77 Extreme4 and a Z87 Extreme4.

 

[Tech Tweaker]

Well, just completed a 2hr stability test at 1.15V (set to 1.18125V in bios) while at stock frequency with prime95. It seems to be stable at this voltage. Might even go lower, but I haven't tried yet.

So, that hasn't changed much being on a different board.

 

[Tech Tweaker]

Seems to be stable at 1.14V (1.16875V in bios) as well, been running Prime95 blend for almost 2.5 hours now.

Temps have gone down a bit since I lowered the vCore, I'm seeing 44-46°C on Core 0 under load and 46-48°C on Core 1 under load.

 

[OptyTrooper]

What do you say we have a little bench off? Your 8400 against mine say CPU-Z,WPirme 32 and Super Pi 1M?

 

[OptyTrooper]

Or maybe a low volt overclock competion.

 

[Tech Tweaker]

And 1.12V was also stable (bios setting 1.15V) for a three hour test on Prime95 blend.

 

[Tech Tweaker]

What do you say we have a little bench off? Your 8400 against mine say CPU-Z,WPirme 32 and Super Pi 1M?

Hmm... I think you may have me at a disadvantage there.

I can't run COLD (Chilled Water/DICE/Single Stage Phase Change/LN2/LHe), so if we were to compete it would have to be ambient cooling only. Otherwise I would be seriously outmatched from the get-go, as I know you like to run sub-ambient.

You probably have more experience with DDR2 tweaking than me, I'm not sure on what your level of experience with the LGA775 platform is though.

Or maybe a low volt overclock competition.

That could be interesting, can't say I've ever seen one of those.

 

[Tech Tweaker]

Seems the lowest it would run and be stable at the stock speed was 1.1v.