What’s a watt? Depends how you measure it. Electrical engineers agree that watts equals volts times amps, but they start disagreeing when measuring the power dissipation of a microprocessor. Power consumption varies with the software workload, which can be anything from a program’s idle loop to a high-frame-rate videogame.
Intel recently provoked controversy while announcing a third-generation Core processor (an Ivy Bridge variant) for ultrathin notebooks and tablets. The company said its new Y-series Core processor will use 7 watts of “scenario design power” (SDP). Nobody had ever heard of SDP, so the general reaction was “WTF?”
Usually, Intel specifies “thermal design power” (TDP). That rating is the maximum power dissipation that engineers should consider when designing the cooling system. TDP isn’t quite as high as “maximum” power (a worst-case rating), but it’s higher than “typical” power (another common but poorly defined specification). So SDP is Intel’s new definition of typical power.
But what’s the scenario? Without specifying the software workload under which the SDP was measured, Intel was telling us nothing. With a light workload, the new processor could sip less than 1 watt. When heavily loaded, it could gulp more than 10 watts. Although the scenario remains vague, the company is admitting some outsiders to its labs to observe power measurements.
Conclusion: The scenario varies. Intel engineers are running many different tasks while carefully monitoring power dissipation and temperatures. The heaviest workloads are graphics-intensive action games, which slow to virtually unplayable frame rates when the Y-series Core processor stays below its SDP of 7 watts. Most other common tasks, including video playback, don’t break this power budget. So, the new processor isn’t an eye-popping game platform, but that’s no surprise.
Generally, Intel’s TDPs are honest. SDP could be a good thing if Intel standardizes the rules and encourages everyone to adopt it.