Overclocking + Undervolting

[Somniferum]

So I got one of those $90 3800+ x2 Toledos for a cheap upgrade from my s939 3500+ single-core. I wanted to overclock it to 2.4GHz, which is the speed I was running my 3500+, to make sure there was no loss in performance in games that may not utilize both cores optimally. No need to push the chip to its limits, at least not yet.

It OC'd to 2.4GHz @ stock voltage no problem, but it was running a little hotter than I would have liked. I explored various cooling options before getting the crazy idea: why not try undervolting it? I didn't expect it to work, but I figured it wouldn't hurt anything to try.

Stock voltage on this chip is 1.3v. My ASrock board allows voltage adjustments in .025v increments.

I was actually able to load Windows all the way down @ 1.2v! However, at that voltage I got a rounding error in SuperPI, so I bumped it back up to 1.25v. At that voltage, it's stable running 2 instances of Prime95 for 12+ hours. This is @2.4GHz (stock is 2Ghz, so that's a moderate 20% overclock).

Temps are not dramatically better, but it did shave off a couple degrees. Mid 30s idle, low 50s full load (dual-prime95).

Has anyone else tried this weird combination? Anything I should watch out for?

 

[RockingDude]

I overclocked my old 6300 to 2.8 and undervolted to 1.1 or so.. shaved off about 10 degrees idle/load.

 

[myocardia]

Originally posted by: Somniferum
Temps are not dramatically better, but it did shave off a couple degrees. Mid 30s idle, low 50s full load (dual-prime95).

Has anyone else tried this weird combination? Anything I should watch out for?

Yeah, it's been tried before. You should watch out, though. With an Athlon 64, you can kill them, if the vcore is too low, compared to the vdimm. In other words, don't overvolt your RAM, while undervolting your cpu.

 

[Somniferum]

Seriously? Can you point me to more info on that? What's the mechanism involved?

On this ASRock board there are only 2 RAM settings, Low and High. Low is 2.5v, and High is 2.7v. I've always just set it to High because I'm OCing the RAM. I guess I could test it out @ 2.5v, if you're not pulling my leg.

 

[myocardia]

Here's a link to a good discussion of that subject. Unfortunately, xtremesystems.org seems to be down at the moment. IIRC, it mostly involved turning off Cool n Quiet, since that reduces the vcore to 1.1v. You should definitely check out that link, once their site is back up again, because they go into detail, but I can't remember the details.

 

[Somniferum]

Interesting, thanks for the link. It sounds like they are talking about much higher vdimm than 2.7 (and I never use Cool n Quiet), but I decided to test out my RAM @ normal voltage just to see. It actually appears to be stable @480MHz (240*2) using 2.5 vdimm, so I might as well leave it there. I previously had to loosen the timings to get it to run at that speed anyway, so I guess that's why it works at stock voltage (this HyperX RAM is rated to run with tight timings but only when overvolted). Thanks again for the info.

 

[Extelleron]

I run my Opteron 144 overclocked to 2.4GHz at 1.3V and I've run it as low as 1.26V... stock is 1.35V or 1.40V, I don't remember. It's interesting to me that it is stable at 1.26V @ 2.4GHz but isn't stable at 2.9GHz at even 1.55V

 

[Dubb]

are there any issues overclocking and undervolting (or just undervolting) a core 2 quad? I've got an x3220 on the way...

 

[MotF Bane]

If you can undervolt and overclock, it's usually a good thing, not all processors can do much of both. On the flip side, my friend's engineering sample E6300 almost died from doing that. It somehow came back to life after a week, but you get the idea.

 

[MarcVenice]

everything is so relative, my mobo on auto settings gives my cpu whatever voltage it wants, up to 1.5 in cpu-z or speedfan, but I oc-ed it and set the voltage at 1.4 So what exactly is undervolting ? Whatever the producer says the chip should run on, or whatever the mobo MAKES the cpu run on when everything is on stock/auto settings ?

 

[Somniferum]

Originally posted by: MarcVenice
everything is so relative, my mobo on auto settings gives my cpu whatever voltage it wants, up to 1.5 in cpu-z or speedfan, but I oc-ed it and set the voltage at 1.4 So what exactly is undervolting ? Whatever the producer says the chip should run on, or whatever the mobo MAKES the cpu run on when everything is on stock/auto settings ?

I would say undervolting is running the chip at a lower voltage than the manufacturer's specifications. If your mobo by default gives the CPU a different voltage than spec, that's a problem with your mobo (or possibly your PSU), I would think -- unless you're using Cool n Quiet or something like that, which adjusts the voltage on the fly.

 

[StopSign]

I lowered my E6300 to 2.4 GHz right now because it's hot in the summer. Back when I was running at 3.2 I had the vcore at around 1.25v. Right now at 2.4 I managed to bring it down to around 1.20. I'll try to lower it some more when I have time.