Every A-level physics student knows the difference between power and energy. But it seems the microprocessor world has yet to make that basic discovery.
The EEMBC has just published its lastest processor benchmark scores which are its first to demonstrate detailed performance and energy tradeoffs using the EnergyBench power/energy metric on a microcontroller.
Four separate benchmark runs were performed to produce scores that isolate the contribution of 208MHz NXP LPC3180 microcontroller's floating point co-processor and instruction cache, together and individually, to device performance, average power consumption, and energy consumption.
The absolute energy required to execute the performance benchmarks decreases by as much as an order of magnitude under the same conditions. However, it was unexpected that the average power also decreased, despite enabling the floating point and instruction cache functions. In addition, average power also varied by as much as 11 per cent based on the benchmark workload that was applied.
"The results underscore that power and energy are two quite different concepts," EEMBC president Markus Levy. "They also show that 'typical power,' a number often provided on CPU datasheets, is a poor indicator of how much energy a device will actually require to perform a specific workload. The take-away for design engineers is the importance of looking at the whole picture when considering tradeoffs between performance, power, and energy."
So what we are saying is: power is the amount of energy transferred per unit of time.
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