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Intel says chip vendors' TDP figures are not comparable

Its Atom and Core TDPs can't be compared
Wed Jan 16 2013, 00:37
An Intel logo on a piece of equipment

CHIPMAKER Intel has said that it is not willing to disclose the workload details used to set its scenario design power (SDP) metric because its competitors do not disclose how they calculate TDP.

Intel courted controversy over Kirk Skaugen's CES 2013 presentation where he announced Ivy Bridge chips that hit 7W using Intel's SDP metric and compared them against Intel's more traditional TDP metric. The firm said that it won't publish the workload profile used to calculate SDP values, claiming that other chip vendors do not disclose how they calculate TDP.

Intel's claims that TDP values are not comparable is big news as many of those who cried foul over the firm's initial mistake - intentional or not - based their arguments on the premise that the TDP metric is calculated to the same standards throughout the industry. Not only did Intel say that chip vendors calculate TDP differently but the firm told The INQUIRER that it calculates TDP differently between its own product ranges, citing its Atom and Core processors as examples.

Adam King, Intel's director of notebook product marketing told The INQUIRER, "At this time we are not prepared to talk specifically [about] what workloads we are using. It is something we haven't disclosed publicly to date and so that would be a pretty big decision for us to do that and we are not prepared to do that today, mainly for competitive reasons. One of the key things about TDP is that there is not an industry standard definition for it. We're not actually quite sure what our competition uses. We know a lot of the phone silicon guys don't appear to specify it at all. So it tends to be a little bit of a trade secret from company to company."

Not only did King say that TDP values are not transferable between chip vendors, he added that TDP figures cannot be compared between Atom and Core processors. He said, "You should note that the Atom processors use a different definition of TDP [than Core processors], one that is more oriented towards mainstream or consumption oriented workloads."

AMD has confirmed that King's comments weren't just a ploy to deflect attention away from Intel's presentation omission. AMD told The INQUIRER that the formula it uses to calculate the TDP ratings of its processors is different from that of Intel, however it didn't disclose the formula.

Given that AMD and Intel have both said that they calculate TDP differently from each other, it might be argued that TDP is equally as meaningless as Intel's SDP metric that it trotted out at CES. After all, neither firm has yet defined how it calculates TDP for its chips, in the same way that Intel is not willing to define how it calculates SDP for its Y series Ivy Bridge chips.

All of this gives rise to the question of what power utilisation ratings consumers and small systems builders can rely on without needing expensive test facilities. Chip vendors should agree upon an open, well documented and reproducible method of measuring chip power utilisation. µ


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