E Stepping Power

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AMD has finally gotten around to releasing 90nm E4 stepping chips in the Opteron level. Here is a list of them.

These are not the first 90nm Opteron chips released, though. Here is a list of those. Compare the two and there is an interesting difference.

The “old” 90nm chips go up to 2.2GHz, and have a maximum wattage of 67 watts. The “new chips” have two wattage standards. Up to 2.4GHz, the maximum wattage is 85.3 watts, and at 2.6GHz, the max is 92.6 watts.

It’s probably safe to say that 67 watts is just about the actual wattage for the 2.2, while 85/92 represent the 2.4 and 2.6. Given that, it looks like the E4 stepping chews up about 10-15% more power than the D4 stepping. That’s not so good, though it’s hardly surprising since these new chip use strained silicon.

On the other hand, the 2.6GHz chews up just seven watts more than the 2.4GHz. While not great, it’s an indicator that wattage doesn’t get out of control with higher speeds like it does with Prescott.

Nonetheless, if you’re hoping in a few months to run an Athlon 64 at 3Ghz, even assuming a modest 10% overvolt and knocking off a few watts for less cache, we’re looking at 120-ish watts.

Is that better than Prescott? Given the increased throughput, it most certainly is. Does that make it a cool-running chip? Hell, no.

We’re looking at about 1.5 watts per sq. mm of CPU core. That’s pretty damn hot, no matter what the fanboys say.

Is it handleable? Yes, with top-end air cooling, but if these chips are capable of much more than 3Ghz, even high-end air may not be enough.

Does this mean you shouldn’t buy one? No, of course not. On the whole, given the circumstances, it looks like AMD has done a fairly good job keeping the heat down using strained silicon, which probably was the straw that broke Prescott’s back.

But you should be prepared.

Understanding SOI: Cooler Does Not Equal Cool

It is simply not true that all SOI chips are cool chips. What is true is that if you run them at moderate speeds, they are pretty cool-running compared to Intel design

Crank up the frequency, though, and the numbers jump. True, they don’t jump up as much as Prescott, but they still jump up a lot. The comparison between Hammer and Prescott isn’t cool vs hot. It is very hot vs. intolerable.

Sorry, but it’s both incorrect and irresponsible to call a 120-watt CPU cool-running. That just sets up anybody who believes it for failure, like saying “you don’t need oxygen to climb Mt. Everest.”

All we’re saying here is “if you plan on making the climb, bring the O2.”

Ed

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