I've seen a couple posts on similar topics, but they all seem to be aiming for relatively low horsepower systems, so I figure I'll give a new topic a try. It's not completely a silentpc question, but nobody else seems to cover this topic exactly, and you guys seem to be the closest.

I'm looking to replace my atom based file server with a machine with quite a bit more power. I got 'burned' by the atom and its horrible high power chipset motherboard, so I'm pretty skeptical of the claims of low power usage out there.

I plan to use this server as a file server, video capture and encoding machine, and game server. Most of the time it'll be idle and I want to optimize for idle power consumption - I'd be happy with the roughly 50 watts that my current rig uses. I don't care how much power it uses when it's actually in use.

I'm tempted to go with the A8 3850 since the reviews that measured it at idling around 50 watts are pretty trustworthy since they didn't install video cards. The problem is that at full bore it's a bit weaker of a cpu than I'd like - it'll satisfy my needs now, but it's not very future proof.

I see lots of claims of sandybridge idling at 4 watts and phenom similarly low, but I can't find any reliable information on low power motherboards since every test out there I've seen has had a video card included and has it idling around 75 watts+.

I almost want to start a review site dedicated to this topic, it's bugging me so much!

Reading around I think the 2400s or 2405s (same cpu, different gpu) look like they may be the way to go. With the 65w TDP I can use a low power intel mobo that another thread managed 22w idle with a 2100T. Benchmarks show the 240xs almost as fast as an i7 930, which is excellent.

It's really simple: most of the idle power consumption comes from the board and the PSU. The situation is not as extreme as with Atoms (current-generation Atom boards are OK when it comes to idle power consumption by the way) but it's basically the same.
So if you want low idle power consumption, get an Intel or MSI board and an efficient PSU. It's that simple. Except that an efficient PSU is not any piece of junk with an "80+" label on it or something. Most PSUs are terribly inefficient at idle. The gold standard is an unconventional design called a pico.
It only gets more complicated if you want still lower power consumption (less than 10-16W, excluding drives). In that case, you need mobile gear (the stuff used in laptops) or a soldering iron and an attitude.

If you're going to use integrated graphics, Intel systems will idle lower. The new AMD chips are good if you want their IGP over Intel's.

I think there's a little more to it than picking an intel or MSI board. You obviously don't need to get a P or Q-series board for a low power integrated video system.

That being said, intel boards are solidly reliable, no doubt. And MSI makes high quality components, too. Stick to the H-series, and you'll be fine.

PicoPSU comments are QFT...

Yeah, I wanted to say one shouldn't focus on the CPU and got carried away. Obviously you want a board which allows you to use the IGP.
And you also want a board with as few unnecessary features as possible (so not a server board unless you need one and so on). You also want to avoid using more RAM than necessary.

Video encoding: fastest is using the Quick Sync on Sandy Bridge and a quad core. Less fast, but nice would be dual core SNB. H67 board would work.

Games: If you can live with low rez gaming, or if your games are mostly CPU bound, get an HD3000 based Sandy Bridge and an H67 board. If you need more gpu power, then get a Z68 board (or find an H67 board with Virtu s/w that allows you to use Quick Sync with a discrete card). So, you still have Quick Sync for encoding and the discrete GPU for gaming. Not sure I know what you mean when you say "game server".

Power:
PSU- most efficient solution is Pico PSU route (if you don't need a high power graphics card). Next is getting a well rated 80+ Platinum or Gold PSU.

Mobo - As others have stated, the Intel mobo's sip the least power.

Most of the Intel Sandy BRidge idle close, so i think you just need to chose how capable you want it to be. I would probably go with 2500K/2405S to get the HD3000 and try without a dedicated GPU, without keyboard, monitor, mouse, im idleing at 14W on my 2100T/H61. When i did the install, with monitor + mouse + keyboard + and fully idle as it was still optimizing, i was around 22W, now to keep it below 50W, the key is to be with a enficient psu for such low loads, like others have suggested a picoPSU or equivalent will be ideal, the problems goes into if you need a dedicated GPU, where the pico might not be enough, but really depends on what gpu are you using.

Btw just out of curiosity, what setup you currently have that you are idling at 50W with dedicated GPU?

Just to mention a few things about the PICO PSU...

You limit yourself by only purchasing a low rating PICO. I own a 90W PICO PSU, because the system that I use that with will max at 60W with two drives running actively in it. I don't need anywhere near that kind of power if I run a single laptop hard drive.

I would suggest looking at Wide Input models of the PICO power supplies, because it will give you an option to run much more efficiently, as well as power higher wattage parts at the same time. Unless my memory is totally off, PICO power supplies should be available all the way up to 220W, if not a little more, so if you were to get a good 16v power brick at around 13A, you'd be just shy of maxing out your PICO. Use some lower wattage components, and you could in theory power a lower end quad core machine, with a mid-range graphics card, all off your PICO. That doesn't even get into what components to specifically use, but there are plenty of options. Low profile is your friend if you're looking for power savings. All the way down to the RAM and hard drive, but you need to define the line where lower power needs to be given up for some form of performance.

The second you start going into video capture and encoding however, that's where you're going to need to make sacrifices of low power for performance. If you were to go with say, an ITX motherboard that's socket 775, some low profile memory, and say, a low end Pentium Dual Core, you could easily idle below 50W, but I'm confused as to what you're really looking for in terms of information. Determine the wattage of video cards, and determine the wattage of the motherboard you want, and add the two together for the answer you're looking for.

Alternatively, I would say you should use software utilities that allow you to downclock your hardware when you know you're not using it. Drop your CPU down to 1.0GHz or lower, drop the GPU way down as well, that's what will make a difference for you. Counting on stock hardware to sit exactly where you want it to is not going to get you the result you're looking for, and you're going to need to "get your hands dirty" so to speak, in order to get the results that you really want.

Regardless, you're going to need either an 80+ or higher power supply to get anywhere close to the numbers you want, and it would be even better to use a PICO in order to save those extra couple, as well as remove heat from the case.

It was my understanding that PicoPSU power supplies need to be 12 volt supplies.

I'm no expert on PICO PSUs, however looking at what mini-box is selling there are 80 and 100W models that are "Wide Input" and allow for 12-32 or 12-25V input.

The Higher wattage one, such as the 200W, which I was mistaken about, is only 12V input. I was pretty tired when writing up that post last night, but I'm not 100% mistaken.

I would say that 12V bricks are pretty common, and some pretty high wattage ones are available, as many users tend to get power from the Dell DA-2 power adapters, available up to 220W or something around that range?

The wide input models are better for lower wattage PICO's, I suppose for people with those odd voltage power adapters lying around, or even for use with laptop power adapters, given the right adapter tip, or some quality time with a soldering iron.

I currently use my PICO 90W with a 40W 12V brick that's commonly used with External Hard Drives, and some lower power LCD displays.

Given some creativity, even some of the other power supplies on Mini-Box could get the job done, with plenty of headroom for an average power build.

Here's a left field alternative. Get a 11" or 13" laptop and use that. Maybe replace the internal drive with an SSD and use an external HDD for data (or just boot from an external SSD). Mobile platforms have the lowest power use. Seems like you could get one that meets your performance needs.

Only as long as you don't take the power consumption of the external drives (with the inefficiency of their PSU) into account. But if 2.5'' drives are sufficient for you file server, a used (possibly broken) laptop is indeed a cost-effective low-power file server... with an integrated UPS!