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Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

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frees the main processor to service other subsystems in an uninterrupted manner.<br />

However, since the buffering is finite, the main processor must service and empty the<br />

buffer with the deadline or connectivity may be lost. To reduce energy consumption,<br />

several researchers [LuCh00] [KrLe00] [OkIs99] [PeBu00] [ShCh99] [PiSh01] [PoLa01]<br />

propose operating the processor at the minimum voltage and frequency that satisfies the<br />

computation deadlines as indicated <strong>by</strong> the kernel or application software. <strong>The</strong> limitation<br />

of this approach is that the deadline must be articulated in the kernel or application<br />

software. Other approaches infer deadlines through measurement and/or classification<br />

[GoCh95] [PeBu98] [WeWe94] [FlRe01] [LoSm01]. Measurement-based feedback can<br />

also be done using not-traditional metrics. Shye [ShSc08] [ShOz08] shows that user<br />

satisfaction can be correlated to per<strong>for</strong>mance monitoring counters and biometric sensors.<br />

Using these metrics, processor per<strong>for</strong>mance can be adjusted to the minimum level that<br />

satisfies the user.<br />

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