An Update On The Linux Power Situation In Ubuntu
Written by Michael Larabel in Software on 7 October 2011. Page 6 of 6. 13 Comments

Fortunately, the EPB MSR being in its normal mode rather than performance mode on these newer kernels didn't affect the OpenArena frame-rate.

With the compute-intensive C-Ray benchmark, the power consumption is up by two Watts on 3.0.1 and Oneiric's current kernel, but drops by two Watts when forcing PCI-E ASPM.

If you were hoping that the PCI Express Active State Power Management situation would be fixed up by the time of the Ubuntu 11.10 release -- considering this issue has been around before the release of Ubuntu 11.04 -- it's not going to happen. Upstream developers have yet to set the ASPM bits directly in more drivers or otherwise figure out how to be more like Windows in terms of how ASPM support is treated. For now, you need to make sure you set "pcie_aspm=force", if your hardware supports the mode. What Canonical's kernel team says is the "fix" to LP #760131 is an unrelated power fix done upstream to ensure that the MSR_IA32_ENERGY_PERF_BIAS register is set to "normal" rather than "performance" mode. The hardware in the original posting to the aforementioned bug report does not even support EPB and is about ASPM and other power changes causing the significantly higher power usage. As these latest tests from the Sandy Bridge notebook show, the 3.0.1+ kernels can improve the power efficiency without degrading the system performance, but will only help you if running the latest Intel hardware that supports the energy performance bias feature.

I'll have some more Linux power information coming soon...

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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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