You're reading from Mastering Embedded Linux Programming - Third Edition

Product typeBook

Published inMay 2021

PublisherPackt

ISBN-139781789530384

Edition3rd Edition

Concepts

Embedded Systems

Authors (2):

Frank Vasquez

Chris Simmonds

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Scaling the clock frequency

Running for a kilometer takes more energy than walking. In a similar way, maybe running the CPU at a lower frequency can save energy. Let's see.

The power consumption of a CPU when executing code is the sum of a static component, caused by gate leakage current, among other things, and a dynamic component, caused by the switching of the gates:

Pcpu = Pstatic + Pdyn

The dynamic power component is dependent on the total capacitance of the logic gates being switched, the clock frequency, and the square of the voltage:

Pdyn = CfV2

From this, we can see that changing the frequency by itself is not going to save any power because the same number of CPU cycles have to be completed in order to execute a given subroutine. If we reduce the frequency by half, it will take twice as long to complete the calculation, but the total power consumed due to the dynamic power component will be the same. In fact, reducing the frequency may actually increase...

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Mastering Embedded Linux Programming - Third Edition

Published in: May 2021Publisher: PacktISBN-13: 9781789530384

Authors (2)

Frank Vasquez

Frank Vasquez is an independent software consultant specializing in consumer electronics. He has over a decade of experience designing and building embedded Linux systems. During that time, he has shipped numerous devices including a rackmount DSP audio server, a diver-held sonar camcorder, and a consumer IoT hotspot. Before his career as an embedded Linux engineer, Frank was a database kernel developer at IBM where he worked on DB2. He lives in Silicon Valley.
Read more about Frank Vasquez

Chris Simmonds

Chris Simmonds is a software consultant and trainer living in southern England. He has almost two decades of experience in designing and building open-source embedded systems. He is the founder and chief consultant at 2net Ltd, which provides professional training and mentoring services in embedded Linux, Linux device drivers, and Android platform development. He has trained engineers at many of the biggest companies in the embedded world, including ARM, Qualcomm, Intel, Ericsson, and General Dynamics. He is a frequent presenter at open source and embedded conferences, including the Embedded Linux Conference and Embedded World.
Read more about Chris Simmonds

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