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Energy Efficient PC's?
eebly asks: "I'm working with a team at my school to help ensure that some of our new building projects are environmentally friendly. As part of that, we want to include good, energy efficient computers. The new building will be labs, so we can't sacrifice power. We're looking for suggestions on what machines use low amounts of power, techniques to make the machines run with less, and ways to tweak the software to make things like sleep mode get used more effectively."
On the CPU side, just about anything besides an AMD or Intel CPU will get you better milage. PowerPC Mac's would be a good place to start. If you are willing to run Linux in the labs, a Netwinder or some of the MIPS-based Cobalt Micro systems would be an option. If you can find a Transmeta CPU powered system you could even run Windows and get decent power.
;-)
On the disk side, the really energy efficient way to go is to use solid-state memory of some kind. That's kind of pricey though, so the next strategy is to use low power hard disks and software which will shut down when not in use.
On the RAM side, I understand both DDR memory and RDRAM have lots of power saving features, although I don't know of a motherboard that is taking advantage of them yet.
More important than RAM though is the display. I think you'll find that going with LCD displays will save you significant amounts of energy.
Gee, doesn't it sound like G4 PowerBook's might be the answer to your problems?
One other thing to consider is software which will do it's best to shutdown idle components of the system. DPMS, ACPI, APM, etc. are all important aspects of getting this right.
sigs are a waste of space
Transformers are inherently inefficient. They lose something like (1-(sqrt(2)/2)) power (sorry, my EE classes were a *long* time ago). Big ones are almost exactly as efficient as small ones.
There is one place where a significant amount of power is lost that could be gained. That area is the transmission line. Electrical losses average out to be the same as the above figure. This power is, esentially, radiated back down the transmission line, and is eventually lost in the form of resistance (heat). Now, all that is needed is to simply impedance match your electrical devices to the transmission line. This can be accomplished using a simple LC circuit.
Of course, every new device you plug in will change the impedance of the transmission line. So the device will have to be able to adapt dynamically.
If you can build a device that monitors the impedance of the power line, then impedance matches it with the electrical device, you'll be rich. Very rich. That is, assuming you can market & sell the damn thing.
--Be human.
Previous posters have noted that LCDs drain less power than CRTs. If you can find ones that are lit by ambient light instead of a backlight, you'll cut power requirements by a huge amount again.
Do a ROM boot off of the network card, and store files on a good file server. Dump in lots and lots of RAM so that you don't miss the swap space (RAM is cheap). Congratulations; you've now slashed another large contributor to the power budget.
Just make sure you're using 100-mbit or better.
Students will use these as CD players, draining power. Ditto sound cards; there's no reason to have them unless you're doing sound editing in the labs.
You don't need the power baggage associated with a kickass graphics card's high clock rates. Unless you're doing hardware-assisted rendering, an old-fashioned card with just 2D acceleration will be fine.
A floppy drive drains power, but is occasionally needed, and isn't used much, so keep it in. Beyond that, most of the frills can go.
There is no need for a patch; you just need an hdparm incantation. In my rc.local, I have a command that looks something like this:
Which spins drives down after 10 minutes of non-use. Repeat as necessary for other drives.
Assuming 7 watts per drive, this kind of spindown will save you around $0.50 per drive per month. For me, that's about $40 per year. Not bad for a few lines of shell script.
When I installed my UPS at home, I went from a 25 minute power backup time with the monitir on, to a 42 minute backup time with the monitor off. That tells me that my monitor (17") is almost sucking up as much as my computer. And my computer isn't the most friendly model out there. The processor is old 1st rev PII 300-MHz heater (I think 40 watts), several SCSI drives and SCSI card, TV tuner card, internal DSL modem, ehternet, ATI Graphics card (with heatsink on the card to illustrate how much power it sucks down) CDROM and CDRW (Granted, the power backup numbers were not while copying a CD, but the point is still valid.)
The answer is to use somewhat aggressive settings on the monitor power off settings (don't bother with screensavers) or to switch to LCD displays.
Now, there is a hughe amount of power drain when the monitor turns itself back on after DPMS off, so you will have a net power loss if the monitor is only shut down for a few seconds at a time, so don't get too aggressive with those settings.
Of course, LCD displays are a more expensive up front cost, but the power savings from them are 2 fold:
First, the display won't be eating up the power.
Second, you won't need to cool the room as much.
That's just my experience. Take it as you will.
-Joe
If you are using Linux boxes, it is possible to do a full shutdown on modern hardware by calling the regular shutdown program from a screensaver like program. One would modify one of the activity moniter programs so it will shut the system down if there is no activity for a period of time. This would shut the system down over night, and durring slow days in the lab.
There is also a patch available that does HD spindown for Linux. From what I hear it now works on IDE drives. That alown will get you 5-10 Watts per machine.
The nightly scripts run by cron can have their run times changed so they are run just after lab close, then an automated shutdown run. Watch that you provide enough spacing between script runs so the previous one's output is available to the next script. This is important for the accounting scripts. You can even do some simple recoding of them to serialize them to shorten the time it takes to get them all done in the right sequence. This would allow one to have cron start them, then the last would shutdown the system when it is finished.