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Why CPU voltage matters, even with reasonable temps.

Soldato
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Every overclocker's nightmare for one of the Tomshardware boys: http://www.tomshardware.co.uk/phenom-ii-x2-555,review-31794-4.html

How Not To Overclock A Clarkdale

There's good news and bad news tied to our overclocking endeavors, as can often be the case when you push hardware harder than it's supposed to go. First, the good news: we achieved a substantial overclock of 4.5 GHz on our retail Pentium G6950 CPU in preparation for this story. We throttled it back to 4.41 GHz to keep the temperatures in check for our benchmarking runs, yielding an impressive 1.61 GHz over the stock frequency.

Now for the bad news: it doesn't count. We killed the processor. Bolstered by reasonable temperature reading and a bit of overconfidence, I pushed the Pentium too hard. My choice of voltage was likely the murder weapon: I set it to 1.475V. In my defense, these are still very new chips, and this is the first G6950 in our lab. There were no warning signs and the CPU lasted through a couple hours of Prime95 testing. Halfway through the overclocked benchmarking runs, the CPU simply died. Not while stress testing Prime95, mind you, but during the AVG virus scan benchmark. Therefore, there will be a follow-up to this article in the next couple of weeks when our replacement arrives. I will be going a second round with the G6950, and this time I'll be limiting myself to a maximum 1.4 V. I will also be testing the CPU on a budget Intel board in the same price range as the Asus M4A785TD-V EVO we used to test the Phenom II X2 555.

Obviously, the results we achieved at 4.41 GHz are not indicative of a sustainable overclock for the components we had on-hand. I did struggle with whether or not to share them in this article. In the end, I decided to include them for curiosity's sake. I know if I were a reader (and not the writer), I would have liked to at least see them. And despite that fact that they aren't really valid from a real-world standpoint, they do give us a glimpse of what a Clarkdale can do at high clocks. It is quite possible that some G9650 CPUs out there might make hit these frequencies more easily with a lower voltage setting.

Looks like Intel recommend a maximum of 1.4v for the Pentium G6950 for a reason. http://www.cpu-world.com/CPUs/Penti...6004593AE (BX80616G6950 - BXC80616G6950).html

At least this wasn't some poor soul at home that had just forked out a couple of hundred on an i7.

Sorry if this has been posted and I'd not spotted it.
 
Could just be a one off... but IIRC gigabyte who I generally consider reliable have a guideline of 1.46v as the absolute maximum for 45nm intel CPUs before this kinda thing happens.
 
The quad core Core i5 and Core i7 are 45NM processors whereas the dual core Pentium G6950,Core i3 and Core i5 processors are 32NM processors.

It just shows that 32NM chips should be kept under 1.4V as Intel has said already.
 
I was wondering when something like this would turn up, seemed bizarre to me that people were feeding them the same voltages that were recommended for 45nm. Odd that it died abruptly rather than degraded, suggests a faulty chip to me.
 
Odd that it died abruptly rather than degraded, suggests a faulty chip to me.

Not really, turn the volts up too much on any electronics and it's bound to fry quickly.
The fact that it did it when not under stress says a lot too, the volts were not drooping so much during that time, not good.
He must have been right on the borderline, got to laugh :D
 
The quad core Core i5 and Core i7 are 45NM processors whereas the dual core Pentium G6950,Core i3 and Core i5 processors are 32NM processors.

It just shows that 32NM chips should be kept under 1.4V as Intel has said already.

Ah I miss-read the specs - glanced down and first thing I saw was 45nm and assumed thats what it was - infact:

Processing Die Lithography: 32 nm
Graphics and IMC Lithography: 45 nm
 
As mentioned Clarkdale is 32nm.

For 45nm I think 1.5V is where it starts to get dangerous, also this goes to show that low temperature is no safety net for high voltage.
 
Low temperature is a safety net against death by electromigration at higher voltages, but electromigration is not the only failure mechanism. Dielectric breakdown perhaps?
 
Hmm...seems odd to me as usually processors are good a little past their VID range. For example wolfdales VID is up to 1.3625V but usually they are fine up to 1.4ish-1.45V. Q6600 VID range is up to 1.5V and many people run them at 1.6V.

So I would expect a VID up to 1.4V to be good for at least 1.45-1.475V?

I wonder what the PLL and VTT settings were?
 
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