Power and Frequency Scaling for the IBM PowerPC 970

A Linux-based power management demonstration for the Maple-D PPC970FX Evaluation System.

Date Posted: September 23, 2005

Overview

Requirements


	1. Do I need special hardware to verify that the system is scaling frequencies correctly?

	2. Is Linux required for trying these routines?

	3. Can I make the system automatically scale frequency to save power?

1. Do I need special hardware to verify that the system is scaling frequencies correctly?

You can use a power meter to check your total system power. As an alternative, you can also run benchmarks to verify that the results change as you would expect with system frequency. For example, you might want to try first running a system benchmark, such as Dhrystone, when the system first boots up. You should expect to see a result similar to the following when the system is initially running at full speed (F) or 1.4GHz:

In order to verify that the processor is running in F/2 mode run, the Dhrystone benchmark test. Again, you should see results similar to the ones we see on our system when running in F/2 mode:


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2. Is Linux required for trying these routines?

No. You can implement power scaling directly from the PIBS loader without Linux.


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3. Can I make the system automatically scale frequency to save power?

In these introductory examples, we demonstrate how to dynamically change the system frequency from the Linux command line prompt. The same code can easily be called from an automatic utility to dynamically scale the system into a lower power state when it is idle. The code for such an automatic utility is available if there is interest.


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Related technologies

For platform(s):
Multi-Platform

For topics:
970, powerPC, power management, linux , cpc925, f/2, MP, frequency, heat, power optimization, scaling

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