Tweaking the work computer to save energy

[Daox]

So, I took my killawatt to work today to see what could be done about saving a little power.

I've already done some things and wanted to know how much they were saving. Unfortunately, there isn't a ton you can do to lower power consumption and new power saving technologies for computers are still being developed and refined. This limited me to only two things, dim the monitor and activate Intel SpeedStep. If you guys have any other ideas feel free to mention them.

I fired up the computer without SpeedStep and took my readings. At idle it was using 210W. So, I enabled SpeedStep and watched the power consumption go down slowly. Unfortunately, this didn't bring it down nearly as far as I had hoped. It would at most dip down to 204W. I was quite disappointed in this as I've read reviews that MUCH more power has been saved with this technology. But, it differs from processor speed to processor speed as to how far the CPU will slow itself down.

Next it was the monitor's turn. At 100% brightness which is way too bright, and the montior was drawing 44W. I dialed it down to 30% which looks way better and it dropped the consumption down to 32W. So, I got a 12W savings there.

All in all I'll be saving 18 watts or roughly 6.5%. This savings over 8.5 hours a day for approximately 37 weeks a year nets me a grand total of 39.6 kWh saved a year. Not much, but if the well over 100 computers in this office all did it we could save around 3,960 kWh a year which doesn't sound as shabby.

[groar]

Originally Posted by Daox

I fired up the computer without SpeedStep and took my readings. At idle it was using 210W. So, I enabled SpeedStep and watched the power consumption go down slowly. Unfortunately, this didn't bring it down nearly as far as I had hoped. It would at most dip down to 204W. I was quite disappointed in this as I've read reviews that MUCH more power has been saved with this technology. But, it differs from processor speed to processor speed as to how far the CPU will slow itself down.

I confirm that on an old PentiumIV : slowing down doesn't change the consumption. In fact I saw the consumption depends on the CPU load. Between 0 and 100% CPU load there was around 40W. When the CPU is faster, the load decreases sooner, but...

...but what the slower speed changed is the temperature. Between high and low speeds there was around 20°C at the CPU level. This is important as in my living room this means a 2°C difference in summer when you come back home => air conditioning saving. For this reason I configure all the linux laptops I manage with the "ondemand" CPU clock manager : the CPU speed is maximal only if the load is big enough.

Next it was the monitor's turn. At 100% brightness which is way too bright, and the montior was drawing 44W. I dialed it down to 30% which looks way better and it dropped the consumption down to 32W. So, I got a 12W savings there.

On laptops this is the secret to make the battery to last longer. During meeting without electric plugs, I set the backlight at the minimum comfortable for my eyes in that room (often 50%) and set the screen to switch off after 2 minutes. Of course just blank the screen, don't launch a CPU hungry screen saver... Now by default I set the backlight at 50%, but increase it if my eyes are needing it.

The processors in notebooks have also a special mode (last laptop processors should have it). By default in C0 they consume at maximum. The lower is the number of interruptions (soft&hard) per second, the deeper the CPU go to sleep. Under Linux I can lower the total number of interruption at such a level the CPU stays in C3 95% of time, but this need the deactivation of some peripherals or functions such as wireless and 3D on some video cards. I also avoid some programs such as firefox with lots of tabs or acrobat reader.

With speedstep management, sleep mode and screen management the consumption of a notebook can be divided by 2.

All in all I'll be saving 18 watts or roughly 6.5%. This savings over 8.5 hours a day for approximately 37 weeks a year nets me a grand total of 39.6 kWh saved a year. Not much, but if the well over 100 computers in this office all did it we could save around 3,960 kWh a year which doesn't sound as shabby.

I changed 2 laptops (run 24x7) by 2 notebooks at home and I saved 140W in continue (+ the consumption of the LCD screen I don't remember) ie 1200kWh/year.

You are lucky when professional computers are switched on only when their users are present... I never saw such a situation.
Lets imagine if modern OS were not loaded with unuseful CPU hungry programs and visual effects. Lets imagine if modern OS were configured to switch the screen off after a while and switch off the computer after a couple hours...

Denis.

[groar]

Originally Posted by groar

Under Linux I can lower the total number of interruption at such a level the CPU stays in C3 95% of time, but this need the deactivation of some peripherals or functions such as wireless and 3D on some video cards. I also avoid some programs such as firefox with lots of tabs or acrobat reader.

Here is my full firefox optimization :

• noscript plugin : do not launch active content (javascript, flash...) by default. You will need to whitelist a lot of sites and domains, but this will permit you to declare domains with bad written active content that eat your CPU or crash your navigator. I'm actively using the status bar icon to set the permissions, first a temporary one (deleted when the navigator is stopped) then permanent if I come back often on the site.
• flashblock plugin : do not launch flash by default. This is the first plugin that I used and permitted me to keep a tab with weather forecast without having a hot CPU (because of a flash showing snow falling ). I keep it as I often want javascript and not flash on a site.
• set image.animation_mode to once (enter about:config as URL). Permit to lower the impact of pages with tens of animated gif. Caution, you may break your navigator if you change something else.

Even if it takes me a little bit more time to visit some sites, I know my navigator is now more responsive and eats less CPU (<10%), permitting the CPU to stay longer in deeper sleep mode (>80% in C2 - on my notebook any USB device prevents the CPU to go into C3) and in low frequency (>98% at 1Ghz instead of 1.8Ghz).

For my own comfort I'm also using the AdBlockPlus plugin, but this is for another reason, the same why I put a "no ad" on my letter box

Denis.

[Daox]

Thanks for the tips groar! I find it interesting that those few things could decrease cpu load that far.