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Ondemand vs. Performance CPU Governing For AMD FX CPUs On Linux 3.17

Michael Larabel

Published on 2 September 2014
Written by Michael Larabel
Page 1 of 4 - 17 Comments

Given recent comments by Phoronix readers, here are some fresh results from the AMD FX-9590 Eight-Core CPU when testing the different CPU scaling governors with the CPUfreq driver on the Linux 3.17 kernel.

In the tests shared yesterday of looking at the AMD FX-9590 CPU on Linux and other CPU benchmarks from this weekend, some Phoronix readers raised concerns about the CPU scaling governor differences between the AMD and Intel hardware. The AMD FX CPUs continue to use the CPUfreq driver by default to handle their scaling while modern Intel CPUs have the new Intel P-State driver. Beyond the Intel-specific P-State vs. CPUfreq, the AMD CPUs generally default to using the "ondemand" governor while with Intel desktop CPUs on P-State it generally ends up with the "performance" mode. Some Phoronix readers found performance vs. ondemand differences to be unfair, but for AMD FX CPUs, there isn't much of a difference in our common CPU torture test benchmarks found in the Phoronix Test Suite.

To clear up any confusion, with the AMD FX-9590 I ran some of the same CPU benchmarks while measuring the impact between CPUFreq's ondemand and performance scaling governors. All benchmarks were handled by the Phoronix Test Suite, which was also measuring the reported CPU temperature and AC system power usage. This data is shared over the next few pages for this eight-core processor that boasts a 4.7GHz base clock frequency and 5.0GHz turbo frequency.

For those that missed it, earlier this year I did an Intel P-State vs. CPUfreq Comparison as an equivalent Intel article to these AMD Linux benchmarks

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