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?"

Kuro Box

[Anonymous Coward]

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. [kurobox.com] It has links to their wiki and forum.

VIA boards work well, but not as fast as Core

[wirelessbuzzers]

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.

Underclocking

[pizza_milkshake]

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 [parseerror.com] 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.

Re:Kuro Box

[harryman100]

This works well as a server, My flatmate recently bought one, and it worked pretty nicely out of the box - he stuck gentoo on it (which took a bit of fiddling), but now has a v low power file/web/subversion server which is on constantly.

However, the power is LOW, don't expect to be able to do much other than just let it sit and serve a few bits and pieces. I bought myself a Via Epia fanless 1GHz motherboard last october, which works as a mythtv front/backend, apache server, subversion server, a synchronisation machine (I have a script on both my other two computers which when run, will rsync all the important stuff, so that all 3 always have everything I need. The board itself takes about 15-17W, + a bit exta to power the PCI card, and the Hard Drive. I haven't measured it yet, but it's saved us quite a bit of money on our electricity because i now only need to turn my desktop on rarely.

The OP seemed to be suggesting he was looking to replace his current machine with a low power option. This is nearly impossible to do without having to make a significant performance sacrifice. What I suggest instead, is going for a low power, always on server to do all the stuff that you need to have available constantly, and then just turn off your powerful machine as often as possible.

A used Pentium-M based laptop

[Jerf]

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.

PC vs Mac electricity consumption

[lancejjj]

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. [blogspot.com]

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.

Re:Don't forget the monitor

[shaitand]

This is my typical recommendation for clients. Power management functions in windows are highly unstable. The PC doesn't wake half the time if you use any power management beyond having the monitor go on low power mode. The monitor uses less power when off then on low power mode.

The advice is simple. Turn off all power management. If you walk away for a second your system will be ready and responsive. If you walk away for 15+min turn off your monitor. If you leave for 8hr+ turn off your PC.

ideas

[bcrowell]

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 [thinkgeek.com], 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.

Re:Two words. PSU & powernowd

[PipOC]

Intel has speedstep technology which does almost precisely the same thing as powernow. Core 2s also have significantly lower power consumption than AMD processors. If you're really into running ultra low power you could run a mobile processor for the desktop, on something like this board http://www.newegg.com/Product/Product.aspx?Item=N8 2E16813202004 [newegg.com]

My Strategies

[the eric conspiracy]

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.

Hackable linux router

[Chris Pimlott]

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.

Re:ideas

[evilviper]

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.

That's an easy way to get energy efficiency, but you can build a desktop more efficiently. 80PLUS PSU, Turion CPU, etc., and your desktop can be lower power than older notebooks, while significantly faster.

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%.

They're most efficient near 100%. HOWEVER, if you're buying an 80PLUS PSU like Seasonic, they have nearly the same efficiency through the whole range. That was one of the parameters for 80PLUS certification.

If you check out the PDFs on http://www.80plus.org/ [80plus.org] they give you a clear graph of efficiency over the range of power draw of all the PSUs they tested.

For your mobo, choose something with integrated video, rather than using a video card.

That won't save you any power at all. A $20 AGP ATI Mobility card will use less power than an integrated chip, and still have better performance.

Another mislead AMD/Intel power comparison.

[John Jamieson]

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)

Re:Don't forget the monitor

[John Jamieson]

I agree, screensavers are a power robber. Not only does the cpu/gpu work harder(thus consume current), the monitors are active as well.

On the other hand, I want to caution that in Monitors or TV's, LCD's do not always save much power per inch of display. It depends on the model. I have one CRT that takes only 30 percent of the standby power of one of my LCD's. Since they are "off" more than on, this negates a lot savings.

An interesting side note, my CRT takes less power when displaying a primarily black screen, my LCD's don't.

Re:Hackable linux router

[John Jamieson]

Good point. Another option is the Linksys NLSU2 or the newer Gigabit Buffalo storage device. Do some homework to figure out how you are going to spin down the hard drives ahead of time. (do you want to buy a drive that supports it, or do it in software)

Re:VIA boards work well, but not as fast as Core

[MojoStan]

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.

Since the anonymous reader wants to "build" the PC, I think a Mac mini recommendation (a good pre-built choice) should be accompanied by the AOpen miniPC barebones series [aopen.com]. The specs and form factor are nearly the same, but AOpen allows a wider selection of components. Systems can be assembled-to-order at MyAOpen.com [myaopen.com]. Barebones miniPCs can be bought at many places like Buy.com and TheNerds.net.

If this form factor is restrictive, then the Mac mini's energy efficient notebook chipset (Intel 945GM) can be had in a microATX motherboard w/PCI Express x16 slot (Asus N4L-VM DH [asus.com], $82 at Newegg), a FlexATX motherboard (Tyan Tomcat i945GM [tyan.com]), or Mini-ITX barebones (MSI Axis 945GM [msi.com.tw]).

Silentpcreview.com

[sgent]

Take a look at Silent PC Review [silentpcreview.com]. 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.

Re:Not one... two.

[AusIV]

I'd also think you could use wake-on-lan to get the lightweight to wake the heavyweight either at predetermined times, or on certain events that would require the heavyweight.

Re:VIA boards work well, but not as fast as Core

[jabuzz]

While a Mac mini is power efficient, the point is that something like a Via C7 mini-ITX is more power efficient still. I recently built an always on device, used a EPIA EN12000G fanless motherboard, with a picoPSU 60W power supply, 512MB of RAM, a 60GB 7200RPM always on rated Hitachi 2.5" drive (you can get up to 160GB 7200RPM laptop drives now), and fitted it in a Pack-BOX enclosure, complete with a PCI Unicorn based ADSL card. They do a slightly bigger version of the case that takes a 3.5" drive or two 2.5" if you want to run RAID1.

This combination is drawing under 20W, and is fanless to boot for added reliability. The whole lot is mounted on the wall under the stairs. While the processor is slower than a Mac mini, it has a faster hard drive and no fans. The next step is to add in a battery backed PSU as an UPS. As the picoPSU can operate on 6-26V, so I don't need a traditional UPS which will be a lot less energy efficient.

Think different... use an NSLU2

[mspohr]

In looking through the reasons you need to have an always-on PC (web or FTP servers, BitTorrent, or simply to make sure I don't miss any messages on IRC or my instant messaging client), it looks like most of these could be done using a Linksys NSLU2 with Linux installed. You will need to fire up another PC to access it but I hope you won't be sitting in front of the PC 24/7.

It uses only about 5w and you can attach flash or USB disks if you need more memory.

http://www.nslu2-linux.org/ [nslu2-linux.org] will tell you everything you need to know to set up the applications you need.

Re:Dont bother.

[smallfries]

I'd agree with your points about the cost of making a new machine versus the savings; but instead of saying don't bother I'd recommend playing with the software a little. Lots of people have "24/7" servers at home for the same applications, but how many people actually use them 24/7? With me it is more a case that I want access 24/7 even if I just use it a few hours a day on average. Have a look at a hibernation kernel and WakeOnLAN. If you can bring the server up to a good point remotely with just 30sec latency then the real power saving is having it shutdown 80% of the time. Using a longhaul governer and scripts you can ensure that it stays up when it needs to (ie during a bittorrent download) but then shuts down when there are no active processes on the system.

powernowd obsolete - use cpufreq ondemand

[Splork]

powernowd and any other userspace cpu freq+voltage managing daemon are long since obsolete.

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 [electricrain.com]. (some BIOSes enable it by default, others do not)

Re:Not one... two.

[MikShapi]

>>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.

Almost.

For fileserver/bittorrent client, use a NEW via C7 that has ONBOARD GbE and is FANLESS. The J7F4 has two GbE, is fanless, (relatively) fast and ultracheap. The EPIA EN12000 or EX10000 or Jetway J7F2+daughterboard are also good, but are more expensive. The former is CHEAP, and you can use the PCI slot for a 4-port SATA card and plug up to 6 SATA drives on the box altogether (2 onboard ports). That's a helluva home fileserver. I run 4 SATA drives on this board as my fileserver, BT clients run on a VNC server on it.Other than 2x80mm fans cooling the 4 drives and the drives themselves, this machine has no moving parts (OS lives on a IDE CF card, power supply is a brick + DC-DC). The box consumes about 40 watts altogether, fans and drives included.

For your PC box you can run on a via config as well, though it's a bit hairier, especially if you want to go hardcore and drop everything that moves. I've decided to take it all the way and build a no-moving-parts vista box. Just to see if I can. And without using the PCI slot for anything (yet).

I've used a via EN12000 board with an LVDS-DVI converter, so I get 2 VGA outputs for my dualhead setup.
It has GbE. It has a 1.2GHz CPU. I'm currently waiting for my 16GB CF card which I got for 200US$ from ebay (8GB should do as well).

I have no clue if the via builtin graphics will run aero. Will know soon though.
Another significant compromise is FAT rather than NTFS, as NTFS writes access times to the drive whenever you READ files, so it'll kill my flash card too fast. Yes, vista can be installed on FAT (with a bit of hacking).
On the same issue, SWAP needs disabling, and any heavy disk IO tasks will need to be configured to use the NAS.

For power supplies on both PC and fileserver I use PicoPSU-120's with 12V/5A bricks. no moving parts there either. The desktop box is estimated to consume around 20-30W for the entire box and should be more than enough for all except gaming and video editing (for that I have tiny lappies with monstrous multicore CPUs). For that there's the C2D 6300 with the 8800GTS, but it's a killer powerhog and is turned off except when used (The Geforce 8800 alone eats over 200W when it's idle!)

For my 2 firewalls (one of which is an AP) I run WRAP 1-2 boards (Geode SC1100 P1-class x86 CPU, not even a heatsink, 128MB and 3 100M nics soldered onboard, plus CF cards for storage) that consume a whopping 3 Watts each.

And the nice thing, if you're used to running 5-10 machines in your home as I've been for the last several years, the power this rig saves pays for the hardware within a couple years.