KDE3 v KDE4 laptop power consumption figures

English Open Chat
1

I’ve done some testing over the last few days regarding power consumption on my HP dv6000 laptop.

The reason for this is that I leave my laptop on overnight sometimes when downloading and seeding torrents (completely legal ones of course ;)), and I noticed that the fan stays on longer and at a higher speed when running KDE4.

This is probably not a big problem on desktop systems, but replacing a fan that has worn out is an expensive undertaking on a laptop.

I did four tests running openSUSE 11.1 with the proprietary Nvidia driver (repo version, not compiled). Two tests running KDE 3, and two running KDE4.2rc1 (installed with the 1-click link from kde.org).

No external components were attached, and on all occasions I had Firefox, konversation, and PySolFC (well I had to do something while waiting!!) running.

While these results are not 100% scientifically accurate, they are nonetheless what I recorded, and you can interpret them in whichever way you choose.

I stopped each test at 20% as this avoids things like the power manager interfering too much. The power manager loves turning the damned thing off without too much notice and I would have lost the time data.

KDE3 (kwin effects enabled) = 121.61 minutes
KDE3 (kwin effects disabled) = 117.98 minutes
KDE4 (kwin effects enabled) = 90.40 minutes
KDE4 (kwin effects disabled) = 112.20 minutes

There were no desktop widgets running on either desktop, the KDE4 desktop was completely bare (all widgets removed) apart from the standard issue menu bar. KDE3 was running the kdetoys3 weather applet if that makes any difference.

I have no idea why KDE3 would last longer with effects than without, it could have been a simple fluke, 3 minutes is not really much difference anyway.

Disregarding these results, the simple fact remains that the fan is considerably louder and stays on longer when running KDE4. I believe the reason is that the graphic card is working harder under KDE4, causing the video chip to heat up and the fan to work harder.

Machine specs:
HP DV6645 laptop
AMD Turion 64x2 1900mhz
2 gigs RAM
160 gig HDD
Nvidia GeForce 8400mGS video
Broadcom 4312v2 wireless adapter (functioning during all tests)
openSUSE 11.1

2

I’m waiting for the day when KDE4 became smart and useful like KDE3 without losing the new sexy plasma style and the power-consuming widgets. :wink:
Useful information, thanks for sharing.

3

Well guess you were expecting a comment like this, but unless you use indentical situations for testing the data is useless.

Hard to do with torrents though as you can’t reproduce the same behaviour. Browsing doesn’t say much either if it’s random use, watching a site with a lot of javascript working the background or playing a flash movie during one session but not the other is gonna cause big differences.

Only conclusion I can come to with the given data is… don’t use kwin effects under kde4 when you value low power use.
See: Example screenshot

4

In this test growbag just compared the power-consuming properties in both KDE3 and KDE4 with or without desktop effects.
And this was the most important part:

KDE3 (kwin effects enabled) = 121.61 minutes
KDE3 (kwin effects disabled) = 117.98 minutes
KDE4 (kwin effects enabled) = 90.40 minutes
KDE4 (kwin effects disabled) = 112.20 minutes

~30 minutes

5

Yes but what if you have a javascript script active doing some fading image gallery or are watching youtube while on KDE3 with the effects enabled and then switch to KDE4 with the effects enabled and only view plain old textpages?

Hard to tell what is to blame unless the test situation is identical or at the very least similar.

6

Oh no, I don’t want to blame KDE4. Growbag wrote

No external components were attached, and on all occasions I had Firefox, konversation, and PySolFC (well I had to do something while waiting!!) running.

The potential program here for power-consuming is Firefox. And because it was a test I hope that growbag in both cases did ~equivalent interactions with his browser.
Otherwise this test was useless. :slight_smile:

7

Firefox use was checking hotmail and reading threads on this forum.

There were NO movies/javascript/flash or anything else running.

There were also NO torrents running at the time of the tests, as I stated earlier, the only major difference was kweather running under KDE3.

The tests were run on the same day, and in this order:

  1. KDE3, no effects
  2. KDE4, with effects, however power manager disabled the effects at 25% battery power
  3. KDE3, with effects
    4, KDE4, no effects

The display was dimmed on all tests, as is normal behaviour when the power adapter is unplugged. KDE4 aldo dimmed the screen further when the power level reached 25% in both cases, KDE3 did not.

I also had no “leaning” toward wanting any particular desktop to “beat” the other, if anything I was hoping that KDE4 would perform close to KDE3 as I do like the KDE 4.2 desktop.

8

So am I reading right that KDE3 with kwin enabled is the longest lasting (more than with it disabled)?

(I don’t know what kwin is, whether it includes any power-saving features or not)

9

KWin effects are the desktop effects in KDE - no power-saving included, maybe in KDE4.3. :wink: