Windows CE.
IEM works in conjunction with the OS and applications running on a mobile device to dynamically adjust processor performance according to varying device demands, according to ARM. IEM controls voltage scaling functions implemented within the applications processor, using "advanced patented algorithms," ARM says. ARM has variously claimed that IEM can produce power savings of
up to 25 percent, and even as much as
75 percent.
i.MX31 power management architectureIntrinsyc's benchmark study measures the benefits of its implementation of ARM IEM software on Freescale's i.MX31 development platform running Windows CE. The paper reports power savings of up to 58 percent under light loading conditions, and up to 25 percent under "heavily loaded" conditions.
The report concludes: "The relatively simple Mean policy used in the tests show IEM provides a power saving of between 9 percent and 58 percent over the condition where no dynamic frequency/voltage scaling is enabled on the iMX31. Power saving is greatest under conditions of low load, and under heavily loaded conditions a saving of 10 percent to 25 percent would be expected. Since typical system use-cases for mobile devices have a great deal of time in near-idle condition, the saving expected in actual operating conditions would be much greater. Savings would be increased using more advanced IEM policies tailored to system, and by combining iMX31 DPTC (process/temperature control) with IEM software-monitored performance level, to control the frequency/voltage performance point."
The Intrinsyc IEM benchmark whitepaper can be downloaded
here (PDF download).
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