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A 4.1 GHz Dual Core at $130?
joshmo97 writes "Tom's Hardware has found that the Pentium D 805 runs stable at 4.1 GHz and outperforms Intel and AMD's flagship offerings in many benchmarks. From the article: 'The Pentium D 805 is a budget CPU, but it puts lots of processors from AMD and Intel to shame. Although it is not based on the latest 65 nm core, this CPU remains stable even when operating at amazing 4.1 GHz. The Pentium D 805 ascends to the throne as the new King of overclocking, knocking out the AMD Opteron 144.'"
It would still be pretty cool if you could use speedstep or whatever to run at a lower speed and lower power most of the time, and then crank it up for a little while when you need the speed, kind of like nitrous injection. This is actually the best automotive metaphor yet because nitrous causes additional heat to be generated :)
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Raise your hand if you've "burned out" a chip that ran stable but was destroyed by overclocking. My Celeron 566 still runs 24/7 at 850 mhz after all these years.
Actually I've been running my old Linux server underclocked for a couple of years now. Athlon 1.4ghz, running at 1ghz. It's much cooler, uses less power, and solid as a rock - even though it lives up in my attic. Apart from a bit of web/database development, and archiving stuff once a week, it really doesn't need much horsepower to serve files and route. Couldn't get it to boot at a lower clock speed though.
Code, Hardware, stuff like that.
You'd be surprised how much "wrong" can happen before you crash. I had faulty ram a while back [well more so it had the wrong timing] and it would boot, run for a while then randomly something would segfault. Then the kernel would panic and lock up, etc.
A simple op like
MOV EAX,[EBX+13]
could excute as
MOV EAX,[EBX+14]
and not result in a significant problem.
As for the self-checks and diodes. You don't have to overheat a circuit to kill it. Over volting a transistor can denature it and you'd never notice. Just like ESD could "partially break" a circuit.
In fact if you looked at a comp lab with open computers chance are at least one IC has some form of ESD damage.
Tom
Someday, I'll have a real sig.
"That sort of underlines the problem with the main point though--any other hardware can go anyways, why is an overclocked CPU of particular concern?"
Because you routinely have to overvolt something to run faster.
Here's EE 101 for this topic...
The frequency is limited by the switching frequency and length of the critical path. The longer the path the more time it takes to charge the wires to get stable transitions. So the remedy is to raise the voltage (hint: think VIR triangle).
So if a circuit (or an instance of the circuit) is rated at say 1.3v @ 2.66Ghz then to run it at 4Ghz you probably have to raise the voltage (unless the limitation to 2.66Ghz was artificial).
Now that we are raising the voltage it's not hard to imagine why it could break the processor.
As for your comment between 3 vs 3.2Ghz processors there are important things you're missing. Processor production is NOT exact. Not only can a run of processors on the same wafer behave differently (hint: is yield 100%?) but between runs the actual process (chemical makeup) can change as they optimize the process.
So no, a 3.2Ghz processor even though it's probably made from the same process that makes 3Ghz shouldn't be suspect.
Tom
Someday, I'll have a real sig.