Unplugging SG-2340/MBT-4220 CPU heatsink fan...

  • As much as I like these little systems, the fan in them is obnoxiously loud.

    On the web, I read someone having simply unplugged the fan to no ill effect.

    According to intel's spec page, provided I understand it correctly, the CPU should have no problems running at up to 110C, which would be 230F.
    (see: https://ark.intel.com/content/www/us/en/ark/products/78475/intel-atom-processor-e3845-2m-cache-1-91-ghz.html#tab-blade-1-0-7 )

    With the fan unplugged, pfSense Dashboard reports a CPU temperature of 75-77C, which would seem to be well below the temperature indicated as permissible by intel.

    Yet the CPU temp graph is in the red:
    Screen Shot 2019-05-20 at 22.15.31.png

    So, is pfSense simply not aware of the CPU specs, and goes to yellow/read at preset temperatures, regardless of what the CPU is capable of, or do I endanger the system by running it at these temperatures for other reasons?

    If this is pfSense not being aware of the CPU specs, should this be considered a bug, or is the green/yellow/red just eye candy that one's supposed to ignore?

  • Personally I would not let any CPU run any higher than 55c. But that just me.

  • Rebel Alliance Netgate Administrator

    I would agree with @chpalmer perhaps figure out another way to get some air movement over the device?

  • I agree the fan should not be unplugged. Even my last decade's spaceheater Core2 Quad overclocked 25% runs at 50c . You're also stressing other onboard components. Check out quieter fans or live with it. https://www.quietpc.com/casefans

  • @chpalmer Just as a comparison: the Core i9-8950HK as a Tj of 100C max, https://ark.intel.com/content/www/us/en/ark/products/134903/intel-core-i9-8950hk-processor-12m-cache-up-to-4-80-ghz.html i.e. ten degrees lower than the CPU in the Atom E3845, yet in my MacBook Pro, it runs in about the same low 70C range under light load, going easily into the mid 80s under high load, as reported by the Intel Power Gadget app.

  • @provels Thanks for the link to quieter fans, will check them out.

    As for stressing other components: the case is well vented otherwise, and stays cool, the CPU does have a heat sink, so it's not like the device as a whole gets hot.

    It turns out, the fan doesn't adapt its speed and is running at full speed at all times. The Minnowboard is according to specs https://minnowboard.org/minnowboard-turbot/technical-specs designed for ambient temperatures up to 40C.
    The dual core version, with 7W instead of 10W, has no fan, just a passive heat sink. So we're talking dissipating an extra 3W of heat at up to 40C that would require a fan.
    I got ambient temperatures at maybe 25C max.

    Anyway, fan is plugged back in, but it would be nice to know if that's really necessary.

  • Netgate Administrator

    I would not run it without a fan. There are options for running the fan at a slower speed.

    I have tested a 12V fan at the 5V the standard fan runs from and it was.... just about OK.


  • @stephenw10 Thanks! If that's electrically not a problem, then that sounds like an option, because generally "low noise fans" start at 40mm and up.

    Unfortunately anything low noise in this form factor seems to either 12V, 3pin, wirelead... just not "5V 2pin" with either magnetic or ball bearing...

    This would seem OK, except for it comes with bare wires:

    Orion OD3510-05LLB
    available at alliedelec (won't let me post a link to the product page, as that's flagged as "spam")

  • Netgate Administrator

    It's impossible to say without testing that specific device. Really it's hard to recommend changing the cooling at all because it was tested with the stock fan and not anything else.

    The fan I tried was from something from China that cost almost nothing but took a month to arrive. It was barely audible at 5V but also barely moved any air!

    It's also possible to run the stock fan at 3.3V. That is quieter and went to 41C at 100% CPU in testing I did. I leave that as an exercise for the user though as I know at least one colleague here who tried it and connected the fan incorrectly toasting it. 😉


  • @stephenw10 Please tell more about the 3.3V option...

  • Netgate Administrator

    Well in your case I don't think it will be possible unfortunately since the 3.3V supply is on the low speed bus connector that has the GPS lure on it.


  • You could cool like this, it’s how I keep my SG-2220 at home really cold. Unplug the internal fan and add a fan kit available on Amazon. This fan kit (sorry, I don’t have a link handy) has a USB connector, two fans, and little stand posts so they sit on, or under, the equipment you’re trying to keep cool.

    I brought the temp of the pfsense box down to 71 F, from about 109 or 110F. The kit, I believe, was about $15 US. You do need to use the USB port on the box itself, or power thru an external power brick, like what charges your cell phone.


  • Here’s the link for the double kit- put 1 fan under, blowing up, put the other on top, blowing up:

    AC Infinity MULTIFAN S7, Quiet Dual 120mm USB Fan for Receiver DVR Playstation Xbox Computer Cabinet Cooling https://www.amazon.com/dp/B00JLV4BWC/ref=cm_sw_r_cp_api_i_mWV6CbVF2KYBN

    There’s also a single fan kit, for a couple bucks less.

    Something like this will make your setup a little bit messy, because of the cables and added bulk of the fan(s), but it could be tied up and dressed up neat. At least it works, and I was surprised by just how much the temp dropped.


  • @akuma1x Cool, in the truest sense of the word!
    Thanks for the pointer!

    By the way: how were you able to post the link? When I even try to post something resembling a link (even php error logs), the forum software flags it as "spam" and prevents me from posting it...

  • Netgate Administrator

    It's the 'reputation' level. I upvoted a few of your posts, you should be good now.


  • @stephenw10 said in Unplugging SG-2340/MBT-4220 CPU heatsink fan...:

    It's the 'reputation' level. I upvoted a few of your posts, you should be good now.

    Ah, thanks! I guess that didn't port over from the old forum software, since I figured I'm on here long enough, but with the switch to the new forum platform, that sort of stuff likely got reset.

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