# Power consumption regression for sandy bridge in 3.0

## DirtyHairy

The following problem has cost me a couple of hours, and I thought that I might create a short post in order to save others the trouble  :Wink:  Updating my laptop (core i7 / HD 3000 IGP) from 3.0-rc7 vanilla to gentoo-sources-3.0.1 caused a serious increase in power consumption of about 3-5 watts. After a bit of research, it turns out that a broken-by-design type power management regression was introduced into the i915 driver somewhere between rc7 and 3.0 final: a deep sleep (from what I gather) state of the GPU was disabled by default as it seems to cause issues for some people. The issue is discussed on https://bugs.launchpad.net/ubuntu/+source/linux/+bug/818830 ; in short, adding the boot option 

```
i915.i915_enable_rc6=1
```

 reenables this features and restores the previous behavior. Hope this helps someone  :Smile: 

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## morpheus2051

Thanks for pointing this out. My laptop runs cooler than before. I did not test the runtime on battery yet. Hope this brings battery life back up again. Since kernel 3.0 is the first kernel with which I do not have any system-hard-locks. But my runtime on battery is not near as good as it is with windows7. On windows7 my system actually runs  about one and a half hour longer than under linux. 

Do you have this parameter enabled?

```

pcie_aspm=force

```

It helped me a little bit.

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## DirtyHairy

 *morpheus2051 wrote:*   

> Since kernel 3.0 is the first kernel with which I do not have any system-hard-locks.

 Same with me, I was getting occasional system freezes with 2.9.39 which is why I switched to the 3.0 release candidates in the first place.

 *morpheus2051 wrote:*   

> 
> 
> But my runtime on battery is not near as good as it is with windows7. On windows7 my system actually runs  about one and a half hour longer than under linux. 

 As I use linux fulltime, I was to lazy to do a direct comparison. However, my machine lasts around 5 hours on linux, which is enough for my purposes.

 *morpheus2051 wrote:*   

> 
> 
> Do you have this parameter enabled?
> 
> ```
> ...

 I tried it when I read about it, but it didn't affect me in any way.

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## albright

 *Quote:*   

> in short, adding the boot option
> 
> ```
> i915.i915_enable_rc6=1
> ```
> ...

 

thanks for that - according to powertop, enabling that option drops my

power consumption by more than a watt (which is quite a lot on my

thinkpad x300, it now - with wireless of and screen half-bright - uses

about 7.5 watts; a couple of watts more with wireless on - I **DO**

wish the iwl4965 driver had powersaving ...)

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