What’s up with the Intel Atom?

Update: I’ve since built a box with a mobile atom CPU which fares much better, as described in this post.

So I was all fired up to lower the power consumption of sandeen.net, the humble server upon which you read this blog.  (And thank you for that, by the way.  You can count yourselves among the 3 finest people on the internet.)

I decided to swap out the old AMD Athlon for an Intel Atom – you know, that low-power, lower-performance wonder-chip from Intel.  I ordered a Gigabyte GA-D510UD from newegg.com, for $90… it looked interesting because it had 4 SATA ports built-in, which should suffice for any amount of storage that I’d likely have connected directly to it.

sandeen.net draws about 51W, which is really not too bad considering there are 2 active drives in it (a mirror) and one sleeping drive that gets backups occasionally.  It’s a AMD Athlon(tm) 64 Processor 3400+ in an old Compaq SR1710NX that I got cheap 5 years ago or so, and updated the cpu, memory, drives, etc…  These new low-power Atoms must be really great then, right?

So it gets here Friday, and I’m all excited… I take down the server, plug it in, and well, first off RHEL5 was not happy with it, bringing the drives up as /dev/hda, /dev/hdb… (remember those?), and and after a bit of fiddling to get the config right I decide to just put things back as they were, and play with the board offline.  Before doing so, I check the Kill A Watt [amzn] … hm, still 51W.  Odd.  Hopefully a newer distro will do some magic power stuff and make it all better.  It’s an atom right?  Low power and all?

So I put the RHEL6 beta on it, and get it all fired up, and re-check … hm, nope, still 36W or so with a single drive, subtract out that 8W, the board is pulling around 27W.  This is not the low power I’d hoped for!  So I start digging – oh look, the chip doesn’t support any P-states, and only 2 C-states:

Cn                Avg residency   P-states (frequencies)
C0 (cpu running)        ( 0.3%)     1.67 Ghz   100.0%
polling           0.0ms ( 0.0%)
C1              137.5ms (99.7%)

And sure enough, checking the Intel docs, only the chips designed for mobile use have the nice power features.

In short, the shiny new low-power Atom sure appears to use just as much power as my 5-year-old run of the mill AMD Athlon64 (in a low P-state, granted).  Sure, at full-tilt maybe it’s using less, but it runs at full-tilt all the time and my Athlon is able to throttle back almost all the time.

I’ll eat the restocking & shipping and send this thing back to newegg, bitterly disappointed.

I have higher hopes for swapping out the hard drives (one leg of the mirror is dying) to WD Caviar Green drives – I can save about 8kWh/month with those if the specs are accurate.  :)

27 thoughts on “What’s up with the Intel Atom?

  1. What? I thought all the Atoms were supposed to be low-power.

    FWIW, josefsipek.net has a quad-core Bloomfield (the Xeon version of i7) which is rated at 130W. Of course the 6 SATA disks eat their fair share.

  2. Michael, I suppose it could be the rest of the gigabyte mobo pulling more power, certainly; I’d like to know what the intel d510 motherboard draws if anyone has one… but there is no doubt that it has no power mgmt capability.

    This certainly is low power compared to, say, a P4, though!

    on edit: ok I shouldn’t say “no power mgmt capability” obviously it has C-states at least.

  3. Eric,

    Which kind of PSU are you using?

    51W is definitely high for the new Atom CPUs. I don’t think the mobo is the culprit here, if you check some reviews around, it should at least draw half power.

    A typical PSU is often very inefficient on low power ranges, DC-DC converters are the way to go to save powers.

    Let us know what is the entire component list!


    • Stefano, it’s an Antec Earthwatts 80plus 380W supply. Which is the same as I used when comparing the wattage on the old socket 939 board…

      Bear in mind that 51W was with 2 spinning drives, probably 7-8W each.

      So with 1 PATA DVD drive, and 2x Seagate Barracuda 7200.11 ST3500320AS drives, and an 80Plus Antec 380W mobo, I came out to right around 51W for both my old 939 motherboard, and the new atom.


  4. the D510 has a TDP of 13W, (
    http://en.wikipedia.org/wiki/List_of_Intel_Atom_microprocessors ) but atoms are often paired with a chipset that uses more than the CPU.

    i looked at some atom mini-itx boards a while ago to replace a via epia board that had died. They all quoted the low CPU power consumption. when i looked at the board layouts i noticed that the biggest heat sink was on the northbrigde, not the CPU.

    i ended up getting a beagleboard. the whole board (CPU, chipset, RAM, SD card) + ac-dc powersupply uses about 1 Watt, measure with a kill-a-watt.

    • @ssam I think it’s fairly well known that the older atom boards had significant northbridge power usage, but I had understood that the d510 + nm10 combination was supposed to be better.

      I suppose to be fair I shoulda measured with a picoPSU, my 380W 80plus PS probably is not so efficient down in the 30-50W range.

  5. @ macaque so that says 20W idle … I guess that’s with the SSD SATA hard drive attached, but that’s effectively 0W :) I measured mine at 27W – the 7W difference could be power supply differences, or maybe the motherboard I guess.

  6. The CPU may not be that green, the motherboard may really suck too much ; but keep in mind that mobos usually come with bad default settings (ie. favouring perfs over power saving, being overly conservative to prevent chocking winxp, …). Such settings may be tunable through BIOS ui, or by telling linux to bypass some ACPI/DMI values.

    Also, the mobo (and the default kernel settings) probably keep powered a few hardware components that you may not actually need (usb ? gigabit ? wol ? audio ? …).

    Wrt C-states :
    Yes, D510 only have two (C0 and C1), cf. http://edc.intel.com/Link.aspx?id=3327 so setting processor.max_cstate=X kernel boot param won’t even help :(

    For the remaining:
    You got hda/hdb ? Isn’t there a BIOS setting to expose SATA links as AHCI
    if so, you can also try ALPM, with ie. echo min_power > /sys/class/scsi_host/hostXX/link_power_management_policy

    Other classical tips for power saving on linux include disabling USB when not needed (or activating usb autosuspend), turning off ethernet wake-on-lan, switching from gigabit ethernet to fastethernet if 100Mbps is enough, disabling the sound system & ac97 codec (or switching them to min_power, they /sys entries for that), activating laptop_mode, …

    • I did do all of those things – ALPM, slow down eth0, set powersave on sound, etc etc etc…

      The main NM10 sata connectors were in IDE mode; there was no way to set them to AHCI in the bios. Gigabyte confirmed this, saying “Unfortunately this is an ITX based board and features are limited on this board” …. right, whatever ;)

      The weird hda/hdb thing seemed to be a misconfiguration though, booting up a RHEL6 root at least gave me scsi device names. :) (The secondary controller, oddly, could be set as AHCI, but not the first). But whether I booted my RHEL5 root, RHEL6 beta, or just for kicks the Meego USB image, I had fairly high power usage – at least, more than I expected.

      In the end, I guess I expected it to be a 10-15W motherboard, not a 25W-30W …

  7. You can actually use P-States on the D510 with linux!
    I use the p4-clockmod as a scaling driver and powernowd daemon to throttle the beast. It goes from 208Mhz to 1.66Ghz with 208Mhz steps.

    I ain’t got a kill-a-watt so I can’t really tell you if it’s doing anything with the power usage.

    I have undervolted the CPU too with the bios.

    Hope this helps

  8. I can tell you that P4-clockmod is doing his job! cpufreq-info and cat /proc/cpuinfo do confrim the frequency change. And as an ultimate test, I run a source compilation with gcc @ 208mhz and then a full 1.66Ghz and I can tell you that there is a HUGE performance difference !

  9. And hooo by the way, with powernowd, 208Mhz is not a fixed freq. So the CPU is running @ 1.66Ghz when needed, and when the job is done, returns to 208Mhz , depending on the actual CPU load.

  10. So, if you were starting from scratch building a low-power NAS box, what would you choose?

    (Speaking as someone who was trying to figure out exactly that, ran across this motherboard, googled GA-D510UD+linux, and wound up here…. Don’t actually care so much about power as noise, as it’d be always-on in a small apartment.)

  11. So. If I got it right, the D510 is allways running at 1.66Ghz and the P4-clockmod is fooling the kernel and even the hardware report of the frequency done by cpufreq-info. crap :/ Too late to send the mobo back anyway.

  12. I actually just swapped my home server to a d510 based setup.

    Previously was:
    generic ecs mainboard
    athlon xp 2000+
    2x 512mb ddr
    realtec pci 8169 nic
    sis pci sata controller
    2x greenpower drives (raid1)
    gentoo linux
    generic video card

    was about 85 watts idle

    swapped out with an intel d510mo board, and a 1gb ddr2 stick. This allowed me to also remove the pci nic, gbit card, and video card.

    new kill-a-watt measurement is 36 watts idle.

    The PSU remains a generic 300 watt atx of unknown efficiency.

    Mine has been a smashing success. Also seemed to be equal or better in performance!

    • Hi Dean –

      36W idle sounds pretty good, and roughly on par with what I saw, I guess, given that I didn’t have low-power drives when I measured. Moving from 85W to 36W will save you > 400 kWh/year, so that’s not bad at all! Which motherboard did you use?

      I guess my point is that my old AMD Athlon is doing just as well – at least when mostly-idle, which it is, most of the time – I now have 2 usually-idle seagate 7200.11 drives, and 2 laptop drives for the main storage, and I’m around 39-40W. So yeah, you’re doing just fine, but I expected the Atom board to shave off even more. I think if it had better power management, it could.

  13. Hi Bruce!

    I’m not sure what I’d use today; having no AHCI mode for the primary SATA adapters really does kind of suck. I think I’d probably lean toward a more mainstream cpu, but find something that is power-efficient at low utilization; this should keep it quiet, cool, inexpensive, and small-carbon-footprinted. Unfortunately I don’t know how to find the above setup anymore; AMD has some low TDP cpus these days but I don’t see them actually for sale anywhere. Maybe just buy the new mac mini server? :)

  14. I found an easier way to test this is with a Kill-a-watt wireless. That way I can compare two side by side at the same time. That way you seeing power surges from your outlets unexpectedly on one and not the other.

  15. Hi Eric!

    I found your blog this morning. I have really enjoyed your posts on the Enphase forums, and thanks for showing the Enlighten API stuff, but that is another topic.

    On the low power home server stuff, I went through that conversion last year to go from 240 watts continuous down to about 20.
    The new server just uses a single SSD but it is backed up…
    Here is the config:
    Habey Mini PC Barebone BIS-6561, Intel Atom 330 1.6G, NVIDIA MCP7A-ION Chipset, Supports 2GB DDR2 SODIMM and SATA II HDD, GeForce 9400M, w/ HDMI + VGA, Support 1080p HD, ICEFIN Fanless Thermal Design.
    1 OCZ Vertex 60 GB SSD.

    Great stuff on the Blog!
    Ken Clifton

    • Thanks Ken! Just posted a new one on the board I want to migrate to. I think I can get to 30W, but with 4 actually spinning disks, and 2T of mirrored storage. We’ll see!

      If I’d waited for the AMD Brazos boards as a friend suggested, it would probably have been even better.

  16. Pingback: How to build an 18W, 4 terabyte, commodity x86 Linux server | Eric's Blog

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