Puzzled over power consumption figures

I have just upgraded my ram from 512kB to 1.5G. I had wondered before how much extra power would be taken by upgrading the ram. Before the upgrade powertop read 9.1-3W and afterwards that wen up to 9.7-8W. I was getting similar readings in both Linpus and Fedora 10 but they seem high compared to some of the figures I see other people claim, ie 8.7 for Linpus. Are the lower figures coming from ssd models? Mine is the 160G hd model.

Secondly, I have seen it recomended to turn off the wifi when not needed to save power. I also tested this in Linpus and found that it only reduced power by about 0.1W (9.6W after upgrading the ram). This doesn't seem to be very much.

I am unsure whether the ram upgrade was a good idea now that I have seen how much power it takes.

 

Yes, the HDD model uses more power. There's a motor that must be spun. The SSD has no moving parts.

I was under the impression that HDD models also included a 6-cell battery -- I wouldn't worry too much about battery life with a 6-cell.

On a 3-cell battery, in my experience 9.7w (versus about 9.3w) only equated to about a 15-minute loss in battery life. It seems like the extra RAM would be worth it.

Let the drive spin down after starting powertop and you'll probably see a slightly lower power usage. I have an SSD, so I don't know where it is, but you likely have an option to spin the drive down sooner -- check kpowersave and maybe update it if it has no such option. There's a good guide up on installing the newest version. Powertop will also tell you if any particular app or daemon seems to be waking often.

Wifi is not nearly as much of a power hog as screen backlighting. Turn it as low as you can handle. Also, the wifi radio at idle uses less power than when it's actively passing a lot of packets.

If it's that big of a deal, you can get batteries as cheap as $30US on eBay. A 9- or 12-cell should last you all day.

 

Thanks for the reply. Mine only has the 3 cell battery. I am going to look into a bigger battery but if the extra ram cuts the life of a 3 cell by 15min then on a 6 or 9 cell it will be 30-45min. The wifi though doesn't seem worth turning off if it takes so little power when using.

 

Hi,

how did you work out losing 30-45 minutes with you get the larger battery? The higher productivity with the extra RAM might be worth it though.