A few days ago I talked about how noisy my new Dell Studio 15 was but I can now report back with the beginnings of a solution to that problem, and it doesn't appear to be ACPI related.
The first clue I needed was that if I switch to the proprietary fglrx drivers for the Radeon the fan quite quickly drops off to a much more reasonable level. It seems the fglrx drivers have issues, however, in particular I get big black patches on my screen. This video corruption happens especially in Firefox, but sometimes in other applications as well. They also appear to screw up my suspend/resume, which is probably even more annoying to me.
The second clue that I needed was that Radeon power management support has only just made it into recent kernels. Thanks to Michael Kirkland for providing me with both of those clues :-)
/sys/class/drm/ I find a whole bunch of stuff, but in particular there are
Looking through the kernel source code I can see that
power_profile can be set to
power_method can be set to either
Trying out all of these values, it seems I get the quietest result with the
profile method and either the
mid profile. The
dynpm method is nearly as good, and I would think it should really be the default for a 'Mobility' chipset. From the detailed benchmarking that Phoronix did I wonder if it shouldn't be the default for everyone.
For myself, I see some small 'tearing' artifacts occasionally when running with the
low profile. These disappear when I run with the
mid profile, and since that seems to have pretty much the same temperature (and noise) results I'll go with that one. Though the laptop often does still make more noise than I would prefer it to, it is no longer annoying everyone in the room.
Not unexpectedly this seems to have a huge impact on power use, too. It appears that the laptop should now give me around 4.5 hours when I do everything I can think of to lower the power use, whereas before it was more like 2.5 hours.
Now I guess I can get back to hacking on DAViCal...