On Tue, Apr 27, 2010 at 8:50 AM, Paul Hartman <paul.hartman+gen...@gmail.com> wrote: > On Tue, Apr 27, 2010 at 10:21 AM, Mark Knecht <markkne...@gmail.com> wrote: >> Computers are a big portion of the bill around here and learning how >> to reduce power is high on my priorities for the next few months. I'm >> not sure how to handle a multi-use box like this. It's an 8-thread i7 >> processor. I was wondering about powering off certain core when the >> machine isn't doing much. Does Intel hardware do that? I need to >> determine how much power is in the processor, the chipset, memory, the >> disk drives. The machine is 3-drive RAID1 using data center drives. >> The WD Green drives just didn't work for RAID. I'm sure 3 drives is >> adding to my power consumption, but maybe they can be spun down more >> often. Myth recordings are currently stored on an external USB drive, >> so that's more power. > > Supposedly enabled and idle cores use even less power than disabled > cores because of the way the i7 handles C6 state. Intel claims power > usage in this state is approximately zero (not even any leakage). > > Enable C1E and EIST in your BIOS (they are powersaving options), > enable CPU frequency scaling in your Kernel and use ondemand governor > (As you would on a laptop). Disable unused network interfaces or SATA > controllers etc. in BIOS. > > NVidia cards using the proprietary drivers have powersaving and > underclocking options (enable the option "Coolbits" in your xorg.conf > and then use nvidia-settings to see these extra options) > > I don't know if PSUs consume more power than necessary. For example if > you have a 650W power supply but could have gotten by with 380W, could > you save energy by using the smaller one? I'm not an electrical > engineer. :) > > My new system has Samsung drives that seem to have a pretty aggressive > spindown time (at least compared to my old ones, which never > spundown). I was concerned about this in my RAID5 but what I have > really learned was how often my disks are idle. The spindown isn't so > aggressive that it happens while I'm actively using the system. > > I am curious if enabling laptop-mode would have any positive effect on > a desktop that has these CPU & HDD power saving features? Or perhaps > disabling swap entirely and putting temp directories in /dev/shm. > Basically the same kind of techniques people having been using on > laptops for years to reduce disk activity and power consumption. It's > an experiment for a rainy day :) > >
Really great info and ideas Paul. Thanks. I've been playing a lot with power measurements here in my home office. I've got three machines each with their own UPS, two internet connections, 5 monitors, a couple of switches. It all adds up. It's been interesting to look at where the power goes. Keep in mind that my incremental power costs right now are $0.42/KWH. For monthly costs I use 24*365/12 = 730 hours/month. 1) Everything shut off except the power strip plugged into the wall. 5 Watts. Just this power strip plugged into the wall driving 3 UPS's that are turned off costs me $1.53/month. For a power strip? (It has a green and red light!) 2) With all the computers and monitors turned off but the UPS's powered on I used about 25 Watts, so that's about $7.50/month. 3) At idle the laptop uses 75 Watts with no external monitors, 125 Watts with a 23" external monitor. IF I have it on 16 hours/ day that's about 2KWH per day or 61KWH/month for a $25 bill. 4) My new i5-661 desktop driving two external monitors actually uses the same 125 Watts as the laptop so that's another $25/month. 5) My new number cruncher based on the i7-980x with 12GB DRAM, 5 hard drives and two external monitors is about double that at 260 Watts. Simply for power consumption reasons I cannot afford to run it 16 hours per day, and I don't need it that much anyway, so I only turn it on when I have a few days worth of number crunching to do. It's probably costing me $10-$20/month since it's on less than 20% of the time. All in all it turns out I'm spending close to $75/month ($1K/year) just in my office! Getting power down is important to me! - Mark
