Dear Ted:
The specifications are for design engineers. These specifications are for those that build these into systems. Reducing max TDP is making the CPU look like it is better than it really is. A Thermal Management Design needs the actual worst case power and thermal output so that he can design a system that delivers the maximum performance for the given criteria (usually the requirements of the product). By lying to these people, Intel is making the CPU go into designs that are unsuitable for the claims they make.
If you design to no more than the P4 specs, you will wind up with a system that will not perform in a power user environment. These units would not work even with a dumb user that uses a client like Seti that performs heavy duty number crunching. That will force the CPU into thermal overload and thus cycle all of the time (it runs in the background chewing up what would be idle cycles). This high performance system will always run at 50% of max speed. Didn't think of that nasty case? And so many now do it, even unsuspecting system administrators.
By giving the real worst case power (and it is very easy to get within 95% of the worst case in many apps that stay entirely within L1 & L2). If Intel wanted to convey that typical TDP is 54W, they could show a speed vs TDP graph showing maximum, typical, and minimum TDP from 0 to 100% rated speed. And they should also specify the min/typ/max temperature that starts thermal cycling. All of this is needed for a design engineer to build a minimal cost system that delivers desired performance under worst case conditions (and these can get quite bad like max voltage, max ambient, nasty app, dusty and dirty environment).
What Intel is hoping is that designers will build in at least a 40% margin so that thermal cycling never occurs. With today's typical do it on the cheap, margins are smaller than they used to be (and getting smaller).
With AMD, they know that if they design exactly to spec, it will work in all conditions at rated speed. With Intel's P4 specs, a design exactly to spec will produce a system that delivers rated speed, only if run in a freezer or in other normally cold places. Users that throw their systems into hot closets and other typical places will get the shaft considering that the price difference between a 500MHz P3 and a 1.5GHz P4 is at least $500.
What would you do, if your brand new car goes only half as fast as the manual states when the temperature is 75F. You ask your dealer and he states that is to prevent overheating in hot conditions. You would be pretty angry. And you would go to your State Attorney's Office of Consumer Protection and charge the Manufacturer with fraud, and anything else they can think of.
This is no different. There is no excuse not to use absolute maximums and minimums in the specs. More info is better than less, but these have always been worst case numbers. This was and continues to be the correct policy. Anything else is unethical, if not downright fraud.
Pete |
