Intel RC6 Support On The Sandy Bridge Desktop

Urban Terror, another ioquake3-based game, followed the trend set by OpenArena and World of Padman.

Overall, as you can see, Sandy Bridge RC6 is a big win. This hardware feature is meant to reduce the power consumption of the graphics core, which it successfully does, but it also has a wonderful side effect of boosting the graphics performance for most tasks. RC6 is just one of the recent performance optimizations for Sandy Bridge. As to why this happens, back in November after I discovered this under Linux, Eugeni Dodonov of Intel had to say the following in an email to me:

From what we have discussed, such improvements could come from several different paths.

The first explanation is that, with RC6 enabled, the graphical card can actually consume much less power (down to 0V), so it leaves more room for CPU to use the non-claimed power to do more processing of its own.

And the second one is that, thanks to additional thermal bonus which we get from the RC6-provided power economy, the GPU frequency has more room for scaling.

So, in both of those case, you receive some performance boost which arises from spare watts which the gfx card leaves for other components to use. As this extra performance happens on demand (e.g., when you need it - when you need some heavy benchmarks or such), it does not affects the idle behavior. And under stress, when the gfx card is pushed to its limit, it gets some additional FPS as well.

Let's hope that RC6 for Sandy Bridge can soon finally be enabled by default in some sane manner within the Linux kernel. At least for Intel's Ivy Bridge, things are looking bright.