Pentium IV study

InQuest has published a study of the Pentium IV. It found that because of the P4's cache design, it uses 4 times the memory bandwith a PIII does on random access data benchmarks. Even on benchmarks which benefit from the larger cache-line size, the P4 shows no benefit due to its higher clock rate. Furthermore, the 1.5GHz P4's thermal diode throttles the part to effectively 750Mhz as soon as power consumption exceeds 54.7W. Without this limitation, a P4's maximum consumption would be 72.9 watts, similar to a 1.33 GHz Athlon's 73 watts.

Comments

Re:So?

[FFFish]

Why would you say Intel is likely to dominate the platform?

Fact: AMD now holds twenty- to thirty-percent marketshare.

Fact: AMD Duron and Athlon processors are now spec'd by all but one mainstream, brand name supplier.

Fact: The latest AMD processors outperform -- and are widely reported as such -- the latest Intel processors.

Fact: AMD K6-2 mobile processors have a 20% marketshare, and AMD K7-family processors are gaining marketshare.

Fact: Intel keeps fucking things up. And I mean *seriously* fucking up. From backing Rambus to failing chipsets to bolloxing up its relationship with their customers... oh, gahd, the list is endless.

So, how do you foresee Intel dominating the platform war? What I foresee is a an ungainly beast of a has-been chip design and manufacturing company, shooting itself in the foot and chopping its own legs off, while an upstart executes cleanly and quickly, soon to overtake it...


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Throttling may be a feature

[Wreck]

The article says that a thermal diode is responsible for triggering the throttled-down performance. But then it also says that the throttling happens due to the power consumption. These are different things: power consumption only causes the temperature to rise if the cooling is not slurping off excess heat fast enough.

Anyone care to comment on this seeming discrepancy?

Assuming that it really is thermal throttling, I would love to see what a good tech site like Tom's might be able to determine about the throttled down CPU when using various heatsinks. If that feature is really there then you should expect more powerful heatsinks give the same temperature as lesser heatsinks, but higher performance.

In other words, it is possible to see this as a feature, not a bug. You get 1.5G when the processor is capable of it. You get half that when you are running hot; but with good enough cooling you should always get the highest performance possible.

"Overclocking" may go away, replaced by "overcooling".

Take this with a grain of salt.

[Distan]

You have to take anything that Bert McComas says regarding Intel with a grain of salt. He is probably one of their biggest critics and I've never heard him say anything positive about their technology.

I'll give you an example: He says that the chip will slow down when you try to extract useful performance from it. He bases this on his misunderstanding of the THERMTRIP circuitry. Yes, it is true that the P4 will dissapate more energy when you make it run a heavier load. Yes, it is true that if the die on the chip gets too hot, the chip will slow down to protect itself. But that completely ignores the fact that it is up to the system vendor to insure that the chip never gets too hot. Right now, I'm looking at a P4 system that I was a designer on. Not only do we have a fansink on the P4 itself, the chassis has four separate fans to dissapate heat, and one of them is a monster 5-incher. There is no way that one of our systems is going to overheat the P4 and cause it to slow down.

Unfortunately, customers don't seem to appreciate thermal management in their buying decisions. But keep in mind that all 1.5GHz P4 systems are not alike.

Re:So?

[Spy Hunter]

If I had to pick one reason why Intel is likely to sell lots of inferior P4s at higher prices than AMD's superior chips, I would have to say: GHz. P4s simply run at higher clock speeds than AMD's and Joe Consumer doesn't know that AMD chips are faster per Hz than Intel's. He'll simply buy the one with the bigger number. And the clueless sales people at consumer electronics stores don't help much either. I'm sure the following conversation is happening in stores across the country right now:
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Clerk: Can I help you?

Joe: Yeah, I'm looking for a computer.

Clerk: Oh, what you want is the new spiffy Intel Pentium IV that has 1.5 GHz!!!

Joe: What's a GHz?

Clerk: It's, uhhh, a thing that tells you how good your computer is. Having 1.5 is really, really good!!!

Joe: Oh, OK. What about that one over there? [points to a less expensive AMD-powered computer]

Clerk: Oh, well, that one only has 1.2 GHz. It's not a bad computer, but I'll tell you, personally, I'd never buy it. 1.2 GHz aren't nearly enough for today's demanding applications such as web browsing and e-mail!!!
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As much as I hate to admit it, Intel made a good decision when they increased the depth of that pipeline: They decreased the speed, but they increased the only thing that matters to computer buyers, the GHz number. What AMD really needs to do is start an advertising blitz showing how much faster their chips are at a lower clock speed (and a lower price). Otherwise, Joe Consumer (and those clueless clerks) will never hear about it.