Videocards and power consumption
Around a year ago, I bought a new videocard (Radeon HD 4870). It
worked very nicely via the
radeon(4) driver, and even the transition
KMS was pretty straightforward. Performance in games was also
pretty good, at least for the games I was playing.
However, I knew it’s a bit of a power hog, especially at idle, so I
always ran the card (under Linux) at low power, via
class/drm/card0/device/power_profile = low. Wall-socket measurements
gave me a somewhat high ~167 Watts of power (whole system).
Recently I learned that 2.6.38 finally supports the Northern_Islands_(GPU_family) desc=“Northern Islands/Barts” chipsets, so I moved to a new HD 6870, mostly for DirectX 11 support (tesselation is shiny!) (even though I don’t have yet any DX11 games). Had to run a rc kernel for a while, which didn’t happen in recent times, but Linux still works nicely (and remember to update the firmware embedded in kernel if you change the GPU!). Also, performance in games is better, but the biggest surprise was the new idle power consumption: just 95W.
Going from 167W to 95W, a ~40% reduction in overall power consumption just by replacing the videocard is surprising to me. Hey, if I would keep my computer powered on all the time for a few years the videocard would actually pay for itself ;-)
Probably when talking just for the videocard itself the change would be more like 60% reduction in idle power consumption. I’m not sure whether to be upset with AMD for the very “bad” old card, or the very good results with the new one :)