Intel Sandy Bridge RC6 Is Good To Go
Written by Michael Larabel in Software on 27 February 2012. Page 5 of 5. 3 Comments

World of Padman, another ioquake3-based game, had results just like OpenArena.

When RC6 was enabled for this Sandy Bridge laptop with an Intel Core i5 2520M CPU with mobile (GT2+) graphics, the power consumption while idling dropped by just under 30%. However, when running any OpenGL test, the power consumption was higher by about 30%.

This is in line with other Phoronix tests shown in previous months where when idling and the GPU is not busy there is significant power-savings, but when the GPU is being taxed with RC6 enabled, the power consumption flips higher. However, this does also result in a graphics performance improvement for many workloads. The performance improvements with RC6 ranged from 10% to just shy of 30%.

Assuming you are not doing much gaming while on battery power, RC6 is still a definite win. Others may desire the ability to have RC6 enabled but when the graphics core is under stress and running on battery power to dynamically disable RC6 in an automated manner so it would run at the normal performance level without increased power consumption. Desktop users also benefit from lower power consumption at idle while increased performance (at a higher level of power consumption) with RC6 enabled. Enabling the deep or deepest RC6 power-states was not of any greater benefit for the hardware under test in this article.

Look for Intel RC6 by default for Sandy Bridge (and Ivy Bridge) CPUs with the Linux 3.4 upstream kernel, the upcoming Ubuntu 12.04 LTS release with its patched Linux 3.2 kernel, and eventually the RC6 work may be back-ported to the other stable Linux kernel branches for the Intel DRM driver. RC6 can also be manually enabled on recent kernels by manually passing the "i915.i915_enable_rc6=1" kernel module parameter.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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