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Building an Energy Efficient, Always-On PC?
An anonymous reader asks: "Like many readers, I find it necessary to leave my home PC running 24/7, for things like web or FTP servers, BitTorrent, or simply to make sure I don't miss any messages on IRC or my instant messaging client. It has been about 3 years since I built my current PC, and keeping it running all the time uses a lot of juice. With my next PC, I would like to do what I can to keep the power-consumption to a minimum, without sacrificing processing power or other features. What should I look for when choosing components for my PC, and what other ways are there to keep the power consumption down?"
Energy efficient in which way? For the sake of the planet or for your electricity bill?
Generally the energy expended into making a product is directly relative to its price (see Marx and Aristotle). Whether the product is fantastically overpriced and the profits are used to fly CEOs around the world in personal jets, or if the product is made in a sweatshop where the workers are obviously not earning that much and have a greatly smaller carbon footprint than others. Every cent you spend is in turn spent on power. So, don't buy an expensive new PC claiming you are saving the planet.
I have such a box myself, it runs MythTV, mldoneky, a webserver, dhcp, samba, mail server... I made it 4 years ago using a cheap 2.4GHz Celeron which is dog slow yet is more than enough for the tasks. On a supply meter it uses an average of 60W. This translates to about £60 of electricity a year ($120).
Say I make a new machine which uses just 40W (unlikely), this machine would have to cost less than £20 per year of usage. In your 3 year cycle you would have to make it for £60 ($120).
Mouse powered Chips, Open source Processors and Lego
Use two PCs. One small Via Epia 700mhz to do your webserver and bit torrent, and another PC with whatever spec you desire to use when you need to do processor-intensive stuff.
If they're networked, you can just as easily copy files over when you need them, or stream media across.
Simple... run Linux on an ARM-based machine - http://www.iyonix.com/
Try replacing a hard disk or two with flash memory, at least for the stable parts of your system (i.e. pretty must unchanging files). I plan to use a CF card along with a CF-to-IDE adapter on my next Linux box, for the generally unchanging parts of my system (/boot, /bin, etc). Not only am I expecting it to make it a faster box, but I expect the power requirements to be much smaller than a hard drive would have been.
Also, passive cooling with heat sinks... no fans = no power running said fans
Let me introduce you to my very own DMCA-protected encryption key: BC 1B 64 4A 8D DE 49 E8 C3 7D CC EE 1A AD EE
1. Buy a good PSU, one that is energy efficient.
2. Run powernowd (with AMD cpus, under linux), which scales down your cpu clock if not under heavy load.
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Be yourself no matter what they say
Using an LCD monitor instead of a CRT will drastically cut your power usage. Turning off the monitor while not at your computer will help as well, instead of just letting the screensaver run. The monitor can consume more power than the PC itself.
I just recently bought a Kuro Box for exactly the same reasons - low power, low noise, always on. You can load it up with Gentoo or Debian, so you can do bittorrent, ftp, http, etc. And it's cheap!
The only downside is that it's headless, but for me that wasn't an issue. If that really bugs you, you can set up a vnc server on it and graphically steer it from your PC.
Check out the kuro website. It has links to their wiki and forum.
For off-the-shelf desktop use, it's hard to beat the Mac Mini. Core duo, notebook hard drive, notebook optical drive, draws like 50 watts at idle. I hear the Acer L320 is going to be similar. No graphics in the Mini, but maybe there will be in the Acer. Good graphics cards are pretty much guaranteed to have high power consumption these days; I'm not sure if you can idle them down.
For light-duty serving, I've been very happy with the latest round of VIA boards (and I've heard the slightly cheaper Jetway variants work just as well). I have an EPIA EN12000EG fanless board running in one of those $30 mini-tower cases from Fry's (or something). The board draws something like 13 watts at idle, and 25 under load. This includes the CPU, RAM and chipset. If you can spin down the hard drives, they'll only be a few watts more, and adding in the PSU inefficiency, it'll be maybe 40 watts AC.
If you just want to serve stuff, you can toss in a 2.5" SATA hard drive (or two, for RAID) and no optical, and fit the whole thing into a case smaller than a Mac Mini, for a lower price than the Mini, with less power consumption than a Mini, even with 2x160GB notebook drives. Or you can put in an optical drive, and it'll be slightly bigger than the Mini.
I've used one of the previous round of these as a desktop machine. Its audio is decent, and as long as you're mostly browsing the CPU is fast enough (compile jobs are slow, but they're much more tolerable with the new C7 proc). The integrated graphics suck, so you won't be gaming on it.
I hereby place the above post in the public domain.
A laptop is already constructed to use as little power as possible, so for non-performance critical tasks, it would probably be quite useful for an always-on server. Built-in UPS is also handy, and it can be tucked away in some closet without taking any room, while still having an emergency keyboard and screen if you need to perform administration tasks on it.
For storage, a couple of USB-drives would be useful, I bet they don't draw much more power than the drive itself.
c++;
Move to man's natural habitat: the city.
And now, a PSA from David Lynch.
... use its Cool'n'Quiet if your motherboard has this CPU and supports it. It's nice when idled and not using the machine so much (e.g., surfing the Web).
Now, if I could make my Windows XP Pro. SP2 stable. Others and I can't figure out why I get blue screens with Cool'n'Quiet enabled.
Ant(Dude) @ Quality Foraged Links (AQFL.net) & The Ant Farm (antfarm.ma.cx / antfarm.home.dhs.org).
Check out your underclocking options on your current machine; I found that Linux's 'ondemand' cpufreq policy governor made a real difference on my machine: http://parseerror.com/~pizza/cpufreq.html You can also check around in your BIOS to underclock your machine; but the disadvantage there is that the change is permanent; with Linux's CPU governors and a modern CPU your machine runs at full clockspeed only when the cycles are needed; I believe Windows has similar options.
Use one of these: http://www.gumstix.com/
Buy yourself a used Pentium-M based laptop. If you don't need to actually use the computer directly, buy one with the screen broken, which tends to make for some darned cheap laptops. You can hook up a monitor to it, which is how you'll put your OS on it. (Remember, laptops have mouse ports, USB ports, and display, so you can use them as a conventional computer just fine, and most laptops have the graphics chips to drive a higher resolution that their native LCD resolution.) The money you save on buying a cheap laptop like that make up for a lot of power bill, especially with the broken screen bonus.
Get the model number of the laptop in advance, cross-reference that with the chip that it uses, then find the power consumption for that chip if you want to double check. I hear the later-model ones are (surprise surprise) more efficient, but they're all pretty good AFAIK.
As somebody else said, the built-in UPC isn't bad, and a Pentium M will have all the power you need for non-floating-point functions; any Pentium M can handle even a moderately-sized website if you wanted.
My home PC server, which I left on 24x365 for email, backup, etc, ended up costing me well over $150 per year in electricity just for the PC (no periferals, monitor, or anything else).
Noticing this cost, I compared a bunch of Macintosh and PCs, as you can see in this article on PC and Mac electricity use.
As you can see, it's pretty easy to see that the cheapest devices can end up costing more in power alone.
If you plan to run an electronic device close to 24x365, factor electricity consumption into your purchase decision. Also factor in devices like cable modems, wireless routers, and so-called "sleeping equipment" - in combination, they can easily put another several hundred to your electricity bill every year. I use an X10 "appliance" controller to truly switch off idle equipment.
My total monthly electric consumption these days is well under 100 KWh.
My 20" iMac with the Core 2 Duo processor uses around 70-80 watts with the display on, and 30-40 watts with the display (but not the entire computer) in sleep mode. That's less than half of what the Dell it replaced used. I'd bet a similar Mac Mini uses the same or less amount of power.
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As several have mentioned, the obvious choice for an always-on PC is a laptop, as long as you don't require a lot of disk bandwidth. Remember that even an old 486-66 can saturate a T1 line, so almost any laptop will do (but get one with a good lithium battery, definitely not NiMH or NiCd).
The added advantage of these older laptops is that their CPUs do not require a fan -- the fan is the number one problem with most PCs. I've had PC's run for *years* continuously without reboots or crashes. Invariably what give out on these things are the fans, power supply or CPU. Higher powered CPUs (500Mhz or greater) generally have fans, although most are regulated, which is good. But many older Pentium laptops didn't need a fan at all... even better.
I've got a couple of websites running off old Toshiba P5-100 laptops -- work fine for what they need to do: webserving, FTP, TELNET, email, etc.
A good option is to get a cheap virtual host. You get root, install what you like, run what you like, and it uses less power - none of yours - because there are several mostly-idle virtual machines on the same host.
Disk space is relatively expensive, and this may not be an option for you if by 'BitTorrent' you mean 'fill up my 500GB hard drive'.
As others have pointed out, if you can find an obsolete laptop, and just dedicate it for your 24/7 applications, that's going to be by far the most energy-efficient solution.
Get a Kill-A-Watt, so you can actually measure how much power various things are using. Until I got one, I had no idea that my computer's speakers were drawing 12 W all the time, even when the computer was shut down.
2.5" hard drives are more energy efficient than 3.5" ones. You need an adapter cable, and also an adapter to mount it in a standard desktop PC's cage. A 2.5" drive is more money for the same storage, but all hard disks are ridiculously huge for most people's needs these days.
Get an 80PLUS rated power supply. The 80PLUS thing means that not only is it efficient, but it's also made in a more ecologically friendly way, without lead, etc. I've heard a lot of conflicting claims about how you should choose the capacity of your PS compared to the power your machine uses. Some people say a switching PS is most efficient if you run it near its maximum capacity, and others say it's most efficient at 50%. I came across something on usenet recently where they actually collected data, and they found there really wasn't any clear relationship. It's dangerous to get a PS that's not rated high enough, because your machine may use an unusually large amount of power during the boot process, and it may boot unreliably if your PS isn't rated high enough.
Try to get all the ACPI power management features of your machine working. Unfortunately, that can be easier said than done. Many BIOSes default to only doing S1 sleep mode, which hardly saves you any power at all. That's because a lot of older hardware can't handle S3.
For your mobo, choose something with integrated video, rather than using a video card. If you're into gaming, this is yet another good reason why you don't want your always-on machine to be the same as your main machine you use all the time.
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I got the "Nehemiah" version, which uses a 60mm fan. I also got a case with a fanless supply (brick + electronics in case) to try to make it as silent as possible.
So, based on my experience, some recommendations:
Turn the monitor off when you aren't using it. An LCD monitor is more energy efficient than a CRT.
Buy a low-end video card. The high end cards are energy hogs.
Use a CPU that you can scale back operating frequency on using CPUSPEED etc when the machine is idle.
Don't buy more CPU speed than you need. Consider buying a low power version of the CPU you are getting.
Consider a motherboard that you can use a portable CPU on.
Buy the smallest feature size CPUs. They are usually more energy efficient.
Use smartd etc. to spin down your hard drives. Right now that usually means IDE drives - spinning down
SATA drives on Linux can be a challenge - it depends on kernel & drivers. Each hard drive = 10 watss
Don't install more RAM than you need.
Get a motherboard that allows you to turn off unneeded stuff like serial ports etc.
Buy an efficient power supply.
Use something like the Killawatt power meter to measure your results.
Switch to compact flourescent bulbs!!
Do all this and you should be able to get into the 60-70W idle range. Since 1W-year
=$1 that is $60/year.
The flourescents will save you at least another $100/year.
Optimizing for low noise and cost based on off-the-shelf parts led me to this setup. It isn't the lowest power setup I can imagine, but noise and power are directly proportional in most cases. My goal was a very low noise, low cost always-on headless server running Linux with fault tolerant storage, at least one Gb NIC and enough processor and RAM to use for common development tasks. Based on measurements performed here and some guess work I estimate this is pulling 40W at idle and I can't hear it a beyond a meter.
MB: ASUS M2NPV-VM. AM2 socket with on-board Nvidia video, SATA etc. Not running a discrete video card is a large power savings.
CPU: Athlon 64 3500+ AM2 Lima core. This is a recent single core CPU from AMD. Easily obtainable from Newegg et al. The nice thing about it is the low TDP of 45W. This approaches portable CPUs while not costing so much. Stable at 1.2V (perhaps lower if I tried) and works well with cpufreq.
Case: Antec NSK3300 MicroATX. Small and quiet. Uses a high efficiency 300W power supply with a non-standard form factor. I doubt this machine can pull enough juice to get the fan moving at full rate. It's silent 99% of the time.
The rest: 1GB of "value ram", a pair of quiet 250GB WD disks and a Intel Gb PCI NIC I got somewhere. If you want to save more power run 1 disk, cut the RAM in half and don't add a fast NIC. Probably just under 30W at that point.
Lurking at the bottom of the gravity well, getting old
It sounds like you leave your computer on all the time, and use it for a variety of tasks, and you are looking for a machine that can do all of that while being easy on the electric bill. This hard to do, as things like high powered CPU's, high end video cards, and lots of storage tend to not be low power. I suggest you get two computers. Get a low power machine, either an old laptop or a P3 and offload all the tasks like the FTP server and the bittorrent duties to this machine, and leave it on 24/7. Old laptops work great for this, as they are built for low power and have a built in UPS. P3 systems also work well, many ex-corporate P3 class systems are quiet, low power, easy to work on, and dirt cheap. Then you get a high power machine, and only have it powered up when you need it. You can have the two computers set up next to each other, and use Synergy to run your IM/IRC on the 24/7 computer while doing whatever on the high end machine at the same time.
If you still must have it all in one desktop machine, one way to cut the power usage if you like lots of storage is to try to only have 1 HDD in the computer, and put the rest on USB/Firewire harddrives which you can then shut off when you don't need them.
Depending on what you want to do, you may be able to get away with using a linux-based router running OpenWRT (or something similar) for some services. You won't be able to have any large local storage (although you can access other drives over the local network), but the power usage would be pretty hard to beat.
Bad idea to use USB drives for low power because they generally do not spin down when idle.
Same is true with most RAID adapters (Areca does support spin down).
- Strip down the hardware. Having another PC is a good place to start, that way you can run a headless server. Disable things you don't need in the BIOS. If your stuff isn't CPU-heavy, consider using a Pentium 2. They can run fanless, which is a nice thing to have in any case. If you can live without optical/floppy drives, disconnect those too.
- Tweak the kernel. cpufreq is quite good, works on a lot of processors and doesn't have much of a performance impact. Remove or modularise any hardware drivers you don't need, since the kernel might decide to keep them powered off if it can't use them. Also enable performance tweaks like DMA in the disk/network stuff.
- Don't run unnecessary software. More unused RAM is more disk cache. Read the documentation on Linux's laptop mode setting too - you can make it force the hard disk to stay powered down and only write every few minutes. If you can, just skip the hard disk altogether and run everything from tmpfs.
If you're still not satisfied, you could try some more extreme methods like disconnecting indicator LEDs.Sorry dude, Core 2s do NOT have significantly lower power consumption than AMD processors.
And even when they do, it is not so spectacular when you factor in the lack of a memory controller. (I like the Core 2, hate the P4)
Sorry, this is a COMPLEX subject. How so? Intel and AMD measure Power needs by a different yardstick. AMD makes many parts, has two different processes, and even on the same process has varying power needs.
The AMD 65nm desktop chips use VERY LITTLE power, often kicking the butt of the core 2 duo, especially at idle.
If you really want to save power on a powerfull x86, you undervolt/underclock a 3600x2 65nm chip. At this point, you will worry much more about the power consumption of your Power Supply, Video Chipset and Hard Drive.
As some have suggested, Plug in a large Flash memory device for files accessed but not updated regularly, spin down the HD after a time delay(HD's have a finite number of start ups), look for an efficient supply, and look at the newer AMD integrated video chipsets.(I think you will find these chips consume much less current than others)
I'd like to echo some of the above points. I was making a NAS server that was to be on 24-7.
1) Dump the high performance GPU. A cheap PCI video card saved me 50W.
2) Seasonic makes some nice 80% efficiency PSUs. Well worth it.
3) Turn off integrated peripherals in the BIOS. Are you using the Parallel ports and serial ports? Lower the bus frequency if you can.
I found that a cron job to turn off the CPU at midnight, along with the auto-turn on timer in the BIOS set to 7:00 also worked quite nicely.
No, I don't trust in god. He'll have to pay up front, like everybody else.
And assuming that your OS will let you spin down the disks that aren't in use, keeping most of your running system on CF will keep things quite and low-powered except when you actually need disk.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
Take a look at Silent PC Review. Although concentrated on silent computing, any power usage produces heat requiring fans -- so they spend a lot of time worried about power/heat as well. The site is focused on building your own pc, so they do a good job reviewing components, 2.5 in disk drives, etc.
I was making a NAS server that was to be on 24-7.
S _server/4507-3382_7-31261848.html
I considered making a NAS, but it was about the time several NAS in a box solutions came out. Lacking space for yet another full size box and concerned about I went with one of the pre-packaged solutions. I settled on one that does run Linux. It uses a Riser filesystem. It supports both the Unix shares as well as SMB, both of which can be shut off. The drive is easly partitioned for mounting an encrypted partition. This works well. A mounted encrypted partition shows just like any other partition. After a power down or shutdown, the encripted shares do not auto-mount. It requires going into the web base admin interface, much like a router, and entering the encrypted volume key to mount it. Nice. A stolen drive protects my data with no intervention. All the regular user/password login's are supported.
http://reviews.cnet.com/SimpleTech_SimpleShare_NA
The truth shall set you free!
One word: laptop.
I picked up an old Dell 1Ghz laptop, added an external HD with a USB enclosure, and plugged in all my gizmos with a docking station. Now it does all my 24/7 tasks, hosts my domain, etc. A PCMCIA -> SCSI card serves up my tape backup. VNC means I can keep it tucked away in my rack (though, technically, it's connected to my KVM too), it's quiet, power efficient, low heat, and a little research ensures it won't explode on me.
Don't get me wrong, it's no speed demon, things run slower than if I used a decent desktop... but really, for something that's on all the time, that doesn't really matter if my backup takes 3 hours instead of 2, or email takes a bit longer to process.
And, with this thing handling all my mundane tasks, I can have my main desktop dedicated to being a solid game machine. Best of both worlds.
Don't try to make one machine do all your tasks. Running all the time to do low-cpu tasks, and being a solid desktop machine, are two different things.
If I knew the wedgies I gave you back in 6th grade would have resulted in this . . . I might have taken a moments pause.
I tried doing this with a laptop. I found that a moderately loaded laptop running 24/7 generates a bit more heat than it can dissipate; it was OK all winter but when the house warmed up in the summer it started having problems. It died while I was trying to figure out what to replace it with; the main board was turning brown from the long heat soak. The answer was a small Pentium-M based desktop machine. With a right-sized power supply, large fans turning very slowly, etc. it's very quiet and uses very little power. This little machine (2 GHz Pentium-M) is running my home controls and weather station, doing frequent FTP uploads of weather data, serving web pages, acting as a home file server, etc. Even running Windows XP (yes, I know) it's rock solid. After almost two years it's never crashed and only gets rebooted when the power fails or an automatic update forces it to reboot. The slow turning fans don't suck in dust bunnies, so it's been totally trouble free. You could do worse...
This has come up on /. before, interesting topic. I was very surprised to find I was spending around 100 bucks a year on just power for my pc. Similar to what was posted above.
/., is to remember to use your fricking battery on the laptop!
If your looking to cut back yer power in a big way, you may wanna check your light bulbs first, cause generally, your going to be using more power there than in a typical pc. For your pc, using a notebook is a good idea. One bit of advice I got from the previous post on
Is there software built into any laptop, that allows you to switch between battery/outlet when either reaches low/high threshold? I have a couple years old hp pavi, which I believe doesn't have anything like that.
Depending on how much CPU grunt you need, you could pick up an old second-hand machine (maybe even for free). Re-use is better than recycling anyway.
My gateway is my old desktop from 1999. Celeron 300, 384Mb RAM, 4Gb + 40Gb disk, 2 network cards, modem. Measured the power usage for 3 months using a proper power meter (spinning wheel one like the power companies use to bill you). Ended up being almost exactly 30W averaged over that entire time.
Like some posters suggest, use a dedicated always-on machine.
You may go even lower than an EPIA processor.
My home server is a PowerMac 8200/100 (100MHz 603 CPU), which runs Debian just fine and draws around 30W according to Kill-O-Watt.
Perhaps you could look into substituting the hard drive with a USB mass storage device (AKA thumb drive). Most modern mainboards support booting to USB and some linux distros are able to be installed onto such devices. USB 2.0 would provide tolerable performance and you can easily add or remove storage space.
It uses only about 5w and you can attach flash or USB disks if you need more memory.
http://www.nslu2-linux.org/ will tell you everything you need to know to set up the applications you need.
I don't read your sig. Why are you reading mine?
Sounds like you didn't manage your own expectations very well. Lacking the time or inclination to design a passively-cooled Nehemiah system, I bought one (See http://www.hexus.net/content/item.php?item=606&pag e=3).
It's an elegant, silent and reliable living-room PC.
-- Foolproof systems do not take into account the ingenuity of fools.
Damn, you're right about speakers. Mine run off a 12W AC adapter, so they've been eating up 12W 24/7. I'm gonna use a power strip with switches and turn them off when I'm away/asleep.
You'd be surprised how much peformance you can get while still having low power consumption, heat, and noise. I just built a PC with the following (power-relevant) parts: a AMD Turion MT37 on ASRock K8NF6G-VSTA motherboard, Dynatron A41 CPU cooler, Powertek 500 RT power supply, and a WD caviar SE 80GB SATA drive. Then once assembled, I've been monitoring it with a Kill-a-Watt power meter...the system draws about 50 watts at idle, and so far hasn't peaked above 72 watts during high processing and disk activity. That's about $200 in parts from NewEgg. It runs super cool, silent, with minimal power draw while still giving you the full capabilities of a full desktop (including expansion, which a laptop doesn't offer).
The real key to it all is the CPU and the hard drive, and not having a horrible power supply with a low PF/power conversion factor. The motherboard and CPU cooler power draw should be fairly consistent and interchangable, although you'll want to ensure you get a Cool-N-Quite compatible AMD motherboard for the Turion. This box only has a 80gb HD...I'm sure you can buy any larger, newer SATA-II HD 7200 RPM and likely have low power draw.
I run a small computer lab, and heat + power draw has always been a factor. I've built many systems around the mobile Athlons and now the Turions, and I've always been impressed. So much that I barely buy anything else now. Intel Core Solo/Duo would be good too, but it's just too hard to ignore the price gap between, say, the AMD Turion MT37 and the cheapest Core Solo on Newegg.
Get a Sempron and underclock it. Check out the Silent PC Review forums for info on good boards and sockets, but IIRC the 3200+ 939 is a good underclocker. Run at low speed and voltage with a high efficiency PSU.
The VIA EPIA boards are all very nice, but when you look at the cost of the board, enclosure, psu etc, you realise it will take about five years to recoup the cost in saved electricity vs the Sempron.
That is the biggest problem with energy efficient tech IMHO - it's too expensive. 25 years to recoup my £10,000 investment in solar panels? No thanks.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
I've recently created a fairly low power, high spec PC. Unfortunately, I needed 64bit, and HW virtualisation assitance, so I couldn't get the power that low.
2x 60G laptop hard disks (1 watt each) as a mirror
3x 500M Maxtor (7 watts each spinning, 1 watt on standby), RAID5 (less frequently accessed data - spun down >90% of the time)
1x Asus N4L-VM (~ 3 watts, 945GM chipset + graphics) "Socket 479" motherboard.
1x Core 2 Duo Mobile T7400 2.16GHz (30 watts full speed / both cores flat-out, but about half this with speed step, and less if idle)
- you could use one of the much lower power ~6 watt ULV (ultra low voltage) Celerons, or Cores.
And when it's idle, it runs http://climateprediction.net/.
If you don't need that much horsepower, go for a VIA MiniITX, or an ARM for your always-on box, as other people have said. All-in ~65watts, not as good as I'd hoped, and I may be able to get it down a bit further using a more efficient PSU, but at least it's doing good science whilst it's on!
I use a "hacked" Linksys NSLU2 to run:
I'm using it with an external USB hard-drive, but its quite possible to use a USB key (in which case it would be totally silent).
One hint - there are several alternative "firmware" packages that you can choose from: I went for "openSlug" which completely replaces the original firmware with a mini linux distro. I'd probably advise going with the superficially more kludgey-sounding "unslung" that keeps the original Linksys (linux-based) NAS system but lets you add packages. It seems to have a better range of packages and keeps the web interface.
If you want something that "just works" rather than a several days of cracking nerdy fun, an increasing number of network-attached hard drives have bittorrent clients, FTP servers etc. out-of-the-box e.g. this (Not a recommendation, just an example).
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
Is probably the most mature low power solution, other alternatives are things like MicroATX etc.
modprobe cpufreq_ondemand
/usr/bin/cpufreq-selector -g ondemand
now tune the up and down thresholds to your liking in the /sys/devices/system/cpu/cpu0/cpufreq/ondemand/* "files" and you're good to go.
Also, for Athlon64 and Opteron CPUs you really should enable clock divide in halt to save even more. For instructions on that read opteron-powersave.txt. (some BIOSes enable it by default, others do not)
Seriously go with the new core 2 duo. It uses way less power than it's predicessor the P4. You can probably get away with about 200 watts less on your PSU. That adds up believe me. Seriously, don't use Vista because it's just a lackluster excuse for something new. It will hopefully go the same route as Melinium Edition and dissapear. Other than that, go nutz man. Build ya some uber-micro!
You have been Koil3d.....end of line.
Not all the monitors are equally good about drawing zero power when switched "off". You may consider having a switch between the wall and the power brick.
Beta is broken and the link to classic doesn't work. Stop wasting our time or there won't be anybody left here.
Appreciate that this is not the answer to your question, but have you considered using alternative energy sources to power your new machine as a means to offset it's operating costs? If your location in the world, environment for the machine and financial means all permit you to do so, how about a couple of photo-voltaic panels on the roof? You could even consider planting trees to offset the cost of component construction. Though I'll appreciate that manufacturers typically don't share "production energy costs" with consumers for many products yet.
One of the reasons for making this suggestion is to point out that no amount of time spent selecting the most energy-efficient components is going to offset their production costs. Then you have to run it. So while I think that selecting energy-efficient items is a very commendable approach, there are other things to consider here.
If ultimate performance is not your goal, build down to a power-consumption specification, then aim to deliver as much of that power by alternative energy as you possibly can. For the production energy costs, consider investing in a carbon soak or offset scheme. Or plant on your own land.
Damn Small Linux ( http://damnsmalllinux.org/ ) has a link to a mini itx store with via chipsets. You could build one of those. Some are fanless. Also immediately change your power supply. I use Antec and their better ones are dead quiet. Get an improved processor fan/heatsink like ones from Zalman. Use a case with good airflow. These will provide some relief and perhaps an energy efficient Hard Drive would help. Try letting it sleep much of the day and if you need it to wake to perform tasks you can schedule them. Steve
Why not use your low-power embedded router as your 'always-on' system?
Grab a Linksys WRTSL54GS or some other supported model and install OpenWRT. From there you can install GNU screen, a torrent client, an IRC client, and an instant messaging client of your choosing. The device has a USB 2.0 port so you can attach a large external hard drive or multi-GB flash drive for your torrent downloads.
You'd have to get use to using CLI tools, or if you so choose, you can engineer something web-based using an embedded web server.
This device can remain on 24/7 and consumes about 7-10 watts. On the plus side, you can also use OpenWRT to apply QoS to your torrent downloads so you can keep rocking your FPS or webcam pauselessly on your power-sapping neon-lit dual SLI Aurora.
Here is my article on my low-power, quiet HTPC. I used an AMD Turion, but a Pentium-M works just as well. My goal was to make a PC that would not overheat even when it was enclosed in my home theater with my DVD player, PS2, etc.
The other option is a Mac Mini, Apple TV, or a laptop.
But, you're still going to have a machine on constantly.
So I suggest instead getting some solar panels, to offset your energy consumption, and keeping the machine for 10 years to avoid incurring the cost of building a new one and the consequent environmental damage.
technical writing / development
Baytech makes serial and ethernet controlled RPC modules. A cheaper approach for home use would be X10 power modules (if you don't want to buy the ones from X10 corporation, there are a a couple of third-party ones that Home Depot sells).
Turning them off will save power but the fact that the adapter is rated at 12w doesn't mean they always draw that much; the simple way to be sure is with a power meter like the kill-a-watt.
Use your router! If your router is supported by any number of the router-distros, you can do those tasks. While using minimal power, since it would be on all the time anyways. If it has a USB port you can attach a hard drive to it. Bittorent? Sure. File server? Yep. Instant messaging? Maybe. Downsides: Headless. SSH for access. Boot another computer to use it, shut it down when done. Limited in many ways but, very economical.
Who depends on IRC and IM so much that they need to leave their computer on 24/7 so they don't miss anything? Wouldn't this fall pretty squarely into the category where people look at you sadly and suggest going outside for some fresh air?
Life needs more saving throws.