Grinding Down Your Computer To Just 8.5 Watts

What can you do to make sure your system is running as efficiently as possible? Take a page out of [Mux’s] book, who went to great lengths to measure and adjust his system for ultimate efficiency (translated). What he ended up with is 8.5 Watts of consumption at idle and about 50 Watts under load. Luckily he posted a six-part series with all of the details.

Some of the changes he made were in software, like reducing voltage to certain hardware by adjusting BIOS settings, and installing display drivers that put the screen into the proper sleep mode. Others were hardware changes like swapping out the power supply with a hacked PicoPSU and removing unnecessary parts from the motherboard like the MAX232 com-port chip. Looks like we need to audit our always-on MythTV box and see if we can apply any of these power-saving techniques.

[Thanks Gijs]

24 thoughts on “Grinding Down Your Computer To Just 8.5 Watts

  1. Someone’s going to say it so I might as well be among the first… I already have this. It’s called a notebook. In fact, my 2008 Macbook reports as little as 5.9 watts at idle and only 12-13 watts with the display active and at the lowest brightness.

  2. Hey there, I was just watching my view counts go up and looking at my google analytics to find out where they’re coming from – seems to be you guys. Thanks! I was actually already in the process of translating and summarizing what I’ve done so far so I could ‘officially’ link to my blog series from english speaking websites, but google translate will do for now :)

    Always hoped this would make HaD. I hope the google translate version makes enough sense to get an idea of what I’ve actually done. The pictures will help as well, I guess.

  3. I really recommend the Antec EarthWatts power supply. It is certified by the 80 Plus program, which means the power supply has an efficiency over 80%. It is also really quiet (despite having a fan) and provides everything you would expect from a good power supply like over-current and short-circuit protection.

    Disclaimer: I don’t work for Antec neither I’m a reseller. I’m just happy with one at home.

  4. Another option would be *nix, Android, or Windows Mobile(?) running on an ARM-based device like a Pogoplug or Dockstar. They probably use less than 8.5 watts at full-speed. Of course, that “full-speed” might not be fast enough for what you want to do…

  5. My work with VIA’s PicoITX systems (screenless) use about 12W wide open from a 12V DC source, and they cost ~$300. I don’t run them idle. I have tasks for them at all times.

    There are many PC104 systems which use very low power too, but the home user probably wouldn’t be interested.

    I admire his work; it was difficult to get through the translation.. but I think the choke point here is with what tasks a computer does. A “Watts per workload” type conversion.

    Another interesting read is how Google builds cluster computers out of shipping containers. Link -> ( )

  6. He used a pico-PSU because normal 80+ PSU’s aren’t that efficient in these power-ranges.
    Even the PicoPSU he used wasn’t that efficient, so he modified that one also.
    And this is a complete system, incl. SSD.

    He also states the most efficient commercial available laptop with equal specs (he could find) isn’t as efficient as this system.

    Now lets hope manufacturers will produce mini-ITX boards as efficient as these. I think there is a market for it.

  7. A classic MAX232 has a typical consumption of 40mW. He should have had a lot of them in the PC to economize so much watts :-D

    More seriously, of course a good supply does a lot for consumption but also putting a smaller graphic card instead of card able to display 10^25 polygons per frame at 200fps…for working on Windows.

    Too bad SSD are very expensive, as they must claim far less energy than mechanical disks.

  8. Liked the hack until last page where he does a _very dirty_ hack on a laptop PSU. Instead of modding reference voltage he mods Feedback (destroying galvanic isolation in the process). I suspect this might be why he was no longer able to pull 130W out of the supply after changing it from 20V to 12V in this way.

    (un)Fortunately my dismay went away when I read that he fried the whole thing in the end.


    I agree. The only thing Desktop can provide over laptop currently is strong GPU. But if you use integrated graphics Laptop should be fine.

  9. The reason Mux doesn’t use an off-the-shelf powersupply like an Antec Earthwatts or a Saesonic x400, is because those are really lousy when they have to provide only 7 watts DC.
    There is no way Mux would be able to get down to 8.5 Watts AC with a supply like that.

  10. The normal PSUs are out of the question for such a mod and it is explained in his blog why. Even an 80+ Gold and whatnot PSU will have a poor efficiency when there is practically no load. And he has faced the same problem as me: there’s no ATX PSUs with high efficiency below 300W. His system would run at 3% load with such a thing and there’s no way this is going to be efficiently handled by the PSU. Below roughly 15% of load efficiency drops dead, usually.

  11. @rasz: yeah, the PSU mod is very dirty and totally unrecommendable. The reason is very dirty as well: the PWM controller uses a tertiary winding – the same one it uses for quasiresonant valley detection – for its DC supply. As the secondary voltage goes down from 20 to 12V, the tertiary winding voltage decreased proportionally and the controller went into UVLO just after starting up. This was the easiest way to solve it, but if I really should just pop on a few extra tertiary windings (which will help with low-load quasiresonant operation as well!).

    Anyone else should just buy the 12V version. I had this one laying around for free, so as long as i’m blowing up stuff might as well use that one. By the way, it’s still functioning perfectly fine. I did blow up the primary MOSFET but that was because I switched out the MOSFET with a better-specced… though defective one I had laying around. It won’t suddenly blow up on its own, it’s electrically perfectly fine.

  12. Want to lower consumption?

    Step 1 – downgrade home server from quad core Athalon II to a Via C7 Saved 100 watts.
    Step 2 – remove the 10 SCSI disks from the raid array and replace with 2 WD green drives. Saved 120 watts and gained 1.5TB more space.
    Step 3 – replace standard Power supply with a Certified 80 gold power supply. saved 20 watts.

    So now my Kill-a-watt has my home server that is running my ASterisk phone system, my bittorrent TV harvester, my testbed LAMP server, and acts as the home NAS for TV and Movies.. Dropped from 340 watts average to 8 watts running normal and 12 watts when running at full load, 2 watts when idle.

    Honestly, the Via C7 and Intel Atom processors are killer for servers and need to be used. Get the high power junk you never really used out of there. You are wasting power for no reason.

    My next step, replace the 3 General purpose PC’s around the house with low cost HP thin clients and build a low power quad core server to feed them.

  13. @fartface: the problem with Atom and C7 boards when used as file servers is their small number of disk ports.
    I find ridiculous that some hardware manufacturers put 6+ports on boards clearly aimed at gaming systems while stripping them from smaller ones. 4+1 ports should be the bare minimum (2+2 RAID1 + 1 system) a server board should have.
    There are SATA port multipliers around that should solve the problem at the price of some performance loss, though.

  14. Would just like to add to the previous two comments – while this is a great mod, and pops to mux for the great hack.

    For those who want low power servers, but without the ninja hacking skills, Via C7 is a good choice. I’m running two mini-servers, mostly doing LAMP and VPN gateway duty, they run somewhere between 8W and 14W average.

  15. @ fartface
    Whether you save power with such a quadcore in the end or not is up to the usage of the 3 PCs. You’ll have an idle PC 24/7 AND a thin client. Unless there’s at least 2 users chances are you just use more power and make some tradeoffs in convenience. Your system’s the same everywhere, but it always feels like a thin client ;)
    I’m running a monstrous quadcore and outsourced some demanding tasks to it, while still not switching to a thin client for various reasons that are all related to performance limits.

    For Atoms and C7 as file servers I’d look for PCI based storage controllers. They often are dead cheap if used and do a good job if the disks aren’t heavily accessed so you meet the PCI bus’ limitations.

  16. without any modification at all, my Acer Aspire Revo draws 64.6 Watts max, since that is all its power supply is capable of putting out :P

    Maybe some specs would help? Sure, it’s impressive if it’s running a super-high-end system that low.

    and, @Cricri, he’s not disabling them, he’s removing them.

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