[Bug 67321] [dpm] rs880: Power usage doesn't drop with dpm=1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=67321

--- Comment #4 from l-1 at dbr.me.uk ---
(In reply to comment #3)
> (In reply to comment #2)
> > Will DPM ever reach the levels of fglrx ?
> 
> I'm not sure what else fglrx does on rs780 off hand.


A suggestion: Stutter Mode

I'm not a linux expert but I've done some ad hoc testing. The results imply
that stutter mode is working on fglrx but not working on r600g.

My hardware is Athlon II x2 240, RS880G + 128MB sideport RAM
Kernel 3.12.9

At idle with the HT bus set to its default 2GHz the wallplug power is:

fglrx 31.7W

r600g 36.2W

If I set the HT bus to 400MHz, in the BIOS, as a crude approximation of
disconnecting the HT bus 80%, I get:

fglrx 31.2W

r600g 32.7W (a reduction of 3.5W)


I read that, when using UMA, it should be possible to disconnect the HT bus 93%
of the time, and presumably even more with sideport RAM.

If my idea is plausible, is it possible to enable stutter mode in r600g?

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