G5 2.5GHz OC'd 2.2GHz?

[invaLPsion]

Before you read further please understand that this thread is not being created to start an argument about what is overclocking and what is not, that said, here you go:

From Croquer Dans La Pomme:

"G5 Bi-2.5 GHz currently delivered were initially envisaged to 2.2 GHz.
It was thus necessary of the watercooler with the system which one
knows to make them hold rate suitably."

(A rough translation)

Surprisingly, this could make sense, these chips do run pretty damn hot. They idle anywhere from 45C-60C and under load they get up to 70C-85C. That's hot!

 

[Makosuke]

It's certainly possible that that's the case, but then it's also quite possible that the chips are only rated at 2.2GHz with a standard heatsink.

That is, I've read that the move to 90nm shrunk the chips enough to significantly increase the heat produced per square mm of chip area; this increased heat density could mean that traditional cooling would only allow the chips to run at 2.2GHz, but that with liquid cooling they can run reliably at 2.5GHz.

I could imagine that being interpreted as "overclocking", but it would be different from IBM officially saying "these are 2.2GHz chips", but Apple figuring out that if they liquid-cooled them they can bump the clock up by 10%. In physical terms, they're both the same thing, but in terms of corporate legalese, they're different--in one case, you've got a chip that is rated to a different speed depending on the cooling method, and in another you've got a chip that is rated at one speed (period) being run at another.

I'm guessing a mis-reading of some situation like this is what prompted this overclocking claim--somebody said "IBM said these G5s can only run at 2.2GHz using traditional heatsinks", and the person heard "These G5s are overclocked 2.2GHz chips" or something like that.

 

[Abstract]

I don't think they're overclocked. To say that they're overclocked implies that the G5 chip they have in there now was never made to be used at above 2.2GHz. Since CPUs are made to be usable over a range of speeds, I think 2.5GHz is probably just the high part of the range.

 

[invaLPsion]

I agree, the dual 2.5 is not overclocked.

 

[Sun Baked]

I agree, the dual 2.5 is not overclocked.

Like the Motorola processor, Apple is asking for an aggressively clocked processor to a higher spec (most likely the 105°C Junction temp number instead of the usual 85°C Junction temp. used by Motorola)

Unlike Motorola, IBM is admitting these processors exist, IBM has at least put up that there a processors at these higher temps.

Apple has pushed the specs on the PowerMac, but it can be done on the PowerMacs -- because there is room for better cooling than something in a more restricted space.

---

Of course the alternative is to look at the speed gap that was always there between the PowerMacs and the iMac/notebooks and ask whether you'd want to be limited to the lower clocked processors for the extra year all the time.

Likely not, the PowerMacs are sold as performace machines and restricting them to the same specs as the consumer machines is pointless.

The machines aren't overclocked, but able to tolerate a performace spec processor.

 

[BrianKonarsMac]

they aren't "overclocked" as in some hacker boy sitting at home with his soldering kit on saturday night, praying to cap 100fps. they are however (IMO) modified chips that were not DESIGNED to run above 2.2ghz with traditional cooling. Apple modified their cooling unit so as to clock the chips as close to the fabled 3.0 as possible. this isn't an overclock in the accepted definition of overclocking, but it is the same thing more or less.

unlike a computer which becomes overclocked (thus voided warranty) these macs are warrantied, so apple must have thoroughly tested these chips to make sure they ran stable enough. can't imagine them releasing bum chips and then having to replace all 2.5 G5s sold because they screwed up and didn't test their stability.