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?"

Comments

Not one... two.

[Baddas]

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.

A laptop

[pipatron]

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.

My build

[TopSpin]

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.

Some ideas of my own

[Ant P.]

I've tried to solve exactly this problem myself. Here's a few things I've tried:

• 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.

Bios

[chriso11]

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.