23 ms·

More than you cared to know about PC fans

175 points by dankamongmen 4y ago

nodoodles 4y ago
Great to know, though more of a Mac fan myself... (sorry)
azalemeth 4y ago
Honestly this isn't more than I cared to know about PC fans. I've worked extensively with industrial appliances and fans are bloody important and underlooked: fan failure is often the step that precedes component failure. The one part of the spec I wasn't aware of was just how insanely high the maximum current draw is; I'm glad that we've made more efficient, longer-lasting, effectively silent air-movers that can fit easily within that power budget.
- rietta 4y ago
  Adding fans to consumer devices that don't have them but should, such as a cable modem, certainly improves its reliability in my experience!
  - Eisenstein 4y ago
    The problem with that is when the fan would block the natural venting if it stops working. These devices are engineered to have the heat move the air through and out of the device, and though a fan will usually do a better job of that, it will ultimately fail. When it does, if the fan body is in the way then the intended convection is blocked and the entire unit shuts down or is damaged.
    - Retric 4y ago
      Cable modems are often placed in poorly ventilated spaces that overheat. So you can get the best of both worlds by including generally unneeded fans which enable the device to function in sub optimal conditions, but can also extend lifespan in better ventilated spaces. The alternative of passive cooling in such spaces is unreasonably expense because only a subset of devices are subjected to such conditions.
      - rietta 4y ago
        I have thought about adding a bathroom style vent fan to the closet that houses the network gear for the house. Exhaust near the top and have a cool air intake near the floor.
        js2 4y ago
        AC Infinity make fans specifically for this purpose: https://acinfinity.com/closet-room-fan-systems/ https://acinfinity.com/closet-room-fan-systems/ Bathroom fans work too if you’re able to vent through the ceiling. I can recommend the Panasonic whisper fans (available under a variety of models with “whisper” in the name). I’m using one to exhaust the warm air from my home theater emitted by the projector. I think it’s this one: https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/retail-fans/whisper-choicetm-ventilation-fan-pick-flowtm-80-or-110-cfm https://na.panasonic.com/us/home-and-building-solutions/vent...
  - post_break 4y ago
    Slow big fans on my home receiver kept it going much longer than it probably would have lasted passively cooled.
    - aidenn0 4y ago
      Can you recommend a fan setup for that?
      - post_break 4y ago
        AC Infinity usb fan on amazon. Silent, but moves enough air, and you can bump up the speed.
- dankamongmen 4y ago
  yeah, if you look at the equations at the bottom, power goes up with the third power in relation to rpm. whippin' and drivin' that much air takes some oomph. connect that fan to any normal motherboard, and you're going to burn out your fan header pretty much immediately (especially since inrush current is probably even higher than the steady state).
  - c_o_n_v_e_x 4y ago
    For those interested, the equations are also known as fan or pump affinity laws: https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.html https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.h...
magicalhippo 4y ago
What I want to know is how a ballbearing-less fan suddenly decides to go brrrrrrr. So far I've been lazy and just replacing them, but I'd be nice to know as they seem fine when I spin them manually.
- hoseja 4y ago
  Are you sure it's not a resonance elsewhere?
  - magicalhippo 4y ago
    Yes, if I run the fan stand-alone it will start to brrrr after a short while.
- HPsquared 4y ago
  I'd imagine the fluid bearing gets a bit worn over time such that it's a bit "looser", i.e. doesn't hold the fan rotor as firmly in a straight/central position. Not enough movement to sense by hand, and no roughness, but enough looseness / free-play to allow a kind of resonant vibration or "wobble" when the fan is spinning faster. Edit: or maybe it's just very slightly worn, has debris in the bearing or something, such that it's out-of-round. I think it's the former though (resonance) as that kind of noise can be intermittent.
- LooseMarmoset 4y ago
  Those kinds of fans typically use a bronze bushing rather than a bearing. These bushings are long-lived, but eventually wear. When the bearing hole enlarges as part of the wear process, the fan rotor shaft now has additional room for lateral movement in the bearing and can oscillate in the the bearing rapidly, causing the "brrrrr" noise you hear. You can often extend the life of such bearings by adding a drop of light machine oil to the bearing (usually you have to pull off a sticker on the back of the fan to access the bearing).
bayindirh 4y ago
Nick Black's personal wiki is a treasure trove. The style is a little terse, but it's a non-issue for me.
- dankamongmen 4y ago
  thanks; this warmed my little hacker heart!
  - bayindirh 4y ago
    You're welcome. I'm pretty glad that I found your (not so) small corner on the net, and bookmarked it. Cheers!
wallaBBB 4y ago
Depth of fan analysis in PSU reviews you could find on jonnyguru beats this by a mile. Too bad jonnyguru site is no more.
rietta 4y ago
Nick has been a prolific writer as long as I have known him. This is some great, esoteric stuff, about fans. I have used case fans in unusual applications not involving a computer but never went deeper than provide sufficient power that it spins full speed. For my own builds, I usually just plugged the fan in without a second thought.
owenversteeg 4y ago
Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel heater blower fan. Ideally I'd be interested in something that's >180C resistant but if there are any other options around say 140C max then I'd also be interested.
- tinco 4y ago
  If $33 is not cheap then maybe not. But I buy my delta fans at mouser or digikey, and they have a wider range of specs than typical consumer websites. They come without connectors though so there's some crimping/soldering required. For our little rendering cluster I bought a bunch of 12.000 rpm fans to cool the rack mounted threadrippers. Worked fine, no watercooling in the rack needed and 4ghz on all cores under load.
  - somat 4y ago
    For some reason I got all opinionated about fans and settled on delta as my preferred brand. I think because delta actually had data sheets. The cool thing is that digikey has the exact fans I want, the downside is that the fans digikey sells have no plugs. I tried once to terminate it myself but I was too cheap to buy the correct tools, so that did not go well. and am now a bit bummed about the whole thing, I found a vendor I can trust to sell me real delta fans.. and they have no plugs. sigh will probably stick with nocturna as a good second best.
- jenscow 4y ago
  I prefer fans that are not heat-resistant. That way, it has more motivation to do its job properly.
  - fnordpiglet 4y ago
    The melting will stop when cooling improves.
ilyt 4y ago
I'm surprised it doesn't mention hysteresis some fans have at low speed. Cheap fans often don't have actual proper speed controller on them which means they might start spinning at say 30% PWM but only stop spinning at 15% PWM. That was probably the thing that surprised me most when I upgraded to nice Noctua, at certain PWM it just started, always, and below that it stopped, always.
- paxswill 4y ago
  Those fans that start at 30% and then allow you to go lower are explicitly allowed by the spec from Intel (linked in the article, sec 3.2 and 3.4).
  - ThePowerOfFuet 4y ago
    Allowance in the spec doesn't mean that behaviour is desirable.
antifa 4y ago
I wish noctua would sell aftermarket replacement CPU fans for laptops. I thought there was something wrong with the loudness of my Dell laptop's fan (with low confidence), but I couldn't gauge that any replacement product wound actually be quieter or cared about noise levels.
- deleted 4y ago
  [deleted]
- nicolaslem 4y ago
  Most laptop parts are specifically designed for a particular laptop model. This is very different from the highly standardized desktop parts. Noctua would be sure to lose money selling laptop fans.
rajup 4y ago
Ah reminds me of the time when I was a kid and my PC would randomly crash and would not start for a while. Turns out the processor fan was janky and would not start occasionally requiring a push with a pen or something to get it going. So the POST process in my case had an extra step: "have human check CPU fan"!
- themoonisachees 4y ago
  Same, but my motherboard actually checked the fan was spinning so post literally involved me checking the fan when told
whalesalad 4y ago
What a coincidence, 4x of the 120mm Noctua Redux fans just arrived this morning and are sitting on my living room table waiting to go into my rig. I love in-depth analysis of stuff like this. How do y'all like to manage (chassis) fan speeds? I have been out of the PC world for so long that I forget all pieces of hardware need to be managed.
- ChoGGi 4y ago
  I use a Corsair commander with a copy of system information viewer
  - whalesalad 4y ago
    Dig the fact that this thing comes with little temperature probes - my current case is probably a little too small for the setup I have right now and I am debugging the temperature zones / airflow. It's a Fractal Define C, i7-12700K, Radeon RX 6750XT OC. Initially my CPU cooler fans (2x) were pointed in opposite directions, lol. Would love a thermal camera, but these probes would probably be just as helpful.
- gregmac 4y ago
  FWIW I used to use software (Speedfan, and later something else I don't remember), but after upgrading to Noctua fans, I found whatever is built-in to the motherboard works just fine and gave up on the complication of software. I'm on my second system like this, and I've found they've both been a good temperature and nearly silent most of the time. Even maxed out, it still seems to be quieter and cooler than it would be with most (cheap) fans.
  - whalesalad 4y ago
    nice, that was what I was hoping to achieve
- MivLives 4y ago
  4 way fan splitter to just let the mobo control it all. I run mini itx so not a lot of fan headers.
Markoff 4y ago
I haven't assembled PC in long time, by now I'd expect you can build passively cooled PC if you use PC just for some regular office job and surfing without gaming and resource heavy apps or we are still not there? Back in the days undervolting was for me for interesting than overclocking to make PC as quiet as possible.
- kadoban 4y ago
  Some passively cooled PCs exist, but they're niche and expensive. It's a lot easier to make one that's quiet, but not silent. Big fans that spin slow and not going crazy with bleeding-edge hardware do wonders. Yeah, if you really want, you can try to underclock/undervolt some things here and there.
  - wtallis 4y ago
    I think it's useful to draw a distinction between a silent computer and one that is merely inaudible. For a typical PC, all you really want is for it to not noticeably raise the noise floor of the office it occupies. Going down the route of truly silent PCs forces severe compromises, and in almost every use case it would be better to have fans, properly configured to always spin, with a minimum speed low enough to be inaudible.
- scns 4y ago
  It is absolutely possible, even with a high performance GPU! [0] A video review by LTT [1] [0] https://www.monsterlabo.com/ https://www.monsterlabo.com/ [1] https://www.youtube.com/watch?v=_jYB-RpkmUc https://www.youtube.com/watch?v=_jYB-RpkmUc
egberts1 4y ago
So looking forward to the incomplete "Form Factor" section!!!
axiolite 4y ago
> "there is no readily-available 24V source from an ATX power supply," This is false. ATX provides both +12V and -12V: * https://pinoutguide.com/Power/atxpower_pinout.shtml https://pinoutguide.com/Power/atxpower_pinout.shtml Hooking them together would provide 24VDC. On a 350W PSU, I see -12V rated to supply 0.3A, which would allow for 24V fans drawing up to 7.2W of power, if desirable. I don't see any reason to prefer 24V fans, however. The current losses over such short ranges are minimal, and I would think the larger economies of scale of 12V devices will keep 12V fans less expensive.
- gnu8 4y ago
  This led me to wonder why we still need the -12V supply - I know the -5V supply was removed a while ago because it was only needed for ISA slots. According to Wikipedia, -12V is for RS-232 ports and PCI slots, both of which are hardly seen on any current motherboards. It should be safe to use it for fans, but 7.2 watts is not very much power. Looking on Mouser, I see 24VDC fans that consume 1 watt or 18 watts depending on speed, so one could easily overload the -12V bus if they are trying to get a lot of CFM. I don’t see a compelling reason to use 24V fans in a PC.
  - iknowstuff 4y ago
    I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.
    - toast0 4y ago
      From what I've read, ATX12VO really is 12V only; peripheral power connectors (sata/molex) will be connected to the motherboard, where the 5v and 3.3v (if needed) will be generated. 3.3V on sata power plugs was never reliably available and was rarely if ever used, and one of the pins was redfined to be a disable pin, so it's usually best for everyone if 3.3V isn't provided at all. -12V for RS-232 is easily generated from +5V or similar sources; max232 chips have been available since the 80s
    - 0cf8612b2e1e 4y ago
amelius 4y ago
How does a fan get power to drive the tach output, if the only power it gets is a pwm signal (which might be low when it needs to switch)?
- mrWiz 4y ago
  Generally the fans are powered with a steady state DC source and the PWM is just logic signaling. If the fan is powered by a PWM source the tach output will not be a clean square wave (but could still be reconstructed, if the PWM frequency is sufficiently higher frequency than the fan's rotational speed).
  - amelius 4y ago
    Well, PC fans come in 3-wire and 4-wire forms, where the 3-wire type has only pwm,tach and GND connections (no DC power).
    - robotguy 4y ago
      3-wire is: TACH, DC, GND 4-wire is: PWM, TACH, DC, GND https://noctua.at/en/what-pin-configuration-do-noctua-products-use https://noctua.at/en/what-pin-configuration-do-noctua-produc...
      - amelius 4y ago
        In practice pwm is used instead of DC.
        wtallis 4y ago
        I can't remember the last time I encountered a motherboard that didn't offer you the choice between DC voltage and PWM for fan speed control. Both are still mainstream options; CPU heatsink fans are almost always 4-pin PWM fans but case fans are very commonly 3-pin DC fans. AIO Water cooling kits also commonly use 3-pin fans, especially when integrating their own fan controller or multiplexer so that they only need to occupy one or two fan headers on the motherboard. (Edit: if you mean that in practice, the motherboard approximates DC voltage control using a PWM-based method, that may be true, but it's beside the point; a 3-pin fan is missing the control circuitry that a 4-pin PWM fan uses, and the 3-pin fan's behaviors like turn-on point will be specified in terms of DC voltage not PWM duty cycle, and you can't drive a 3-pin fan with the PWM signal intended for a 4-pin fan because the voltage and current supplied are both far too low.)
deathanatos 4y ago
The pinout is wrong, is it not? As it is drawn, if you mate the two connectors, the wires won't match up. (You'll need to mentally rotate it: the hook on the back of the male connector slots into the rails on the front of the female connector to make them impossible to separate without destroying a nail.) I think the female side is right, it's the male connector that's reversed.
- pwg 4y ago
  > The pinout is wrong, is it not? Not if both connectors are drawn looking top-down. Note the ribbing and clip on the female connector, the bottom of the female connector is at the bottom of the drawing. You'd mate these by lifting the female straight up, rotating about 90 degrees along the vertical axis, and pushing down onto the male connector. And when mated that way, the labeled pin-outs line up perfectly.
  - deathanatos 4y ago
    Oh, you're right; it's drawn such that the business end's holes for the pins are hidden on the bottom; the wires should be coming out the top, but they're not rendered. (So, the pinout is right.) (Edit: in my defense, the CAD model's square holes on that end are pin holes, not wire holes, which would almost certainly be wider, not square, and take up more of the space available on that side, and do on the connector I have. Hard to find a photo on Google, as nobody photographs the non-business-end…)
deathanatos 4y ago
Also, one thing I've always wondered: why do people want to use hwmon to set fan RPMs? (Or really, why do this from userspace at all?) It seems inherently dangerous to me, as you're asking a process who might not receive CPU time for whatever reasons from the very much not realtime OS to control a fan; if the current RPM is too low, and the system starts generating heat, but the fan controlling process doesn't get CPU time … then what happens? It seems to me you want fans controlled with something dedicated to it. The other thing I don't get is all the plethora of options my motherboard gives me to set fans only to fixed RPMs. Am I crazy in that I want the fan to be controlled by heat? (More heat => more RPMs. Keep the system cool, but if there isn't much thermal load, spin the fans down and reduce the noise?) But by fixing an RPM, it seems the only valid input is "100%"; anything else could be too low under stressful conditions. I could also have a cheap motherboard. (I definitely won't be purchasing from this manufacturer again, and the motherboard does have other severe quality issues…)
- MaulingMonkey 4y ago
  > It seems inherently dangerous to me In the old days, it kinda was - at least to your hardware. Then people realized that blowing up components because a fan failed, or became unplugged, or a filter clogged with dust, maybe wasn't a great user experience and/or caused more in-warranty returns that required replacing hardware ($$expensive$$!), and implemented thermal throttling and thermal cutoffs. Nearly two decades ago at this point, I helped a friend diagnose his computer randomly turning off. It turned out to be a CPU fan unplugged itself, causing overheating to trigger a thermal cutoff. No other apparent harm done. Fans aren't the only means of limiting heat: slowing stuff down and turning stuff off also works. And it turns out users sometimes would rather stuff run slow than run loud, and maybe your crappy motherboard vendor shouldn't be writing a ton of code running in kernel space - with all the potential stability and security issues that might entail - for whatever network-connected bloatware syncs your RGB lighting and fan settings to the cloud. And they will do exactly that, if that's what's required to give their customers what they want. Just exposing fan RPMs to userspace might be far less dangerous.
  - deathanatos 4y ago
zajio1am 4y ago
One sad thing with fans in PC is how bad is fan controller / SuperIO driver support in Linux. AFAIK, there is no autodetection for SuperIO chips (like there is for PCI or USB devices) and for many chips there are no drivers anyways. Seems like using USB connected microcontroller with open-source firmware instead of embedded SuperIO seems like easiest way to have reliable fan control in PC.
fiat_fandango 4y ago
Just when we thought Linus Tech Tips had exhausted every normie, low effort way to "investigate" which fan is best to cool a consumer CPU and GPU for gaming...
- dankamongmen 4y ago
  not at all what i was trying to investigate, but thanks
tristor 4y ago
This was a great read, I have always had a love of PC fans, and the technology behind them. It'd quite a complicated engineering challenge to produce a high static pressure, high rate of airflow, and minimize noise while maintaining high reliability. I'm one of those folks that has no problem dropping significant money on fans every time I do a PC build, and so far I have very very rarely ever had a fan fail on me, even after decades of running at high duty cycles. The thing I always marvel at is how high the draw is for some of these fans. At one point I even retrofitted a system with an external radiator for water cooling that used 120V 120mm Panaflos and was separately powered from the computer. I wish folks took cooling more seriously. There are so many devices that benefit from active cooling but rarely get it, or even being strategic around placement, positioning, and mounting to make convective cooling more effective. Thermal limiting is such a common occurrence on modern electronics if you don't give due consideration to cooling, as we've moved towards more passively cooled devices, including PCs (laptop especially).
rkagerer 4y ago
This is great. I determined some time back the most important thing I need to know is "buy Noctua". They're expensive but have consistently outlived all other PC fans I've ever tried.
Scene_Cast2 4y ago
One interesting thing to note is the P/Q fan curve. It plots how much air a fan, at a specific PWM frequency, moves against a variable restriction (measured in pressure drop). Here's a sample - https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-f12-and-nf-s12a https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-... Hypothetically, knowing the heatsink airflow curve, one can find the amount of air a fan will move across. There are PQ curves (either reported or measured) for a bunch of fans and some radiators out there.
dankamongmen 4y ago
hey neat, i'm glad people enjoyed this (i'm the author)! this was all due to my inaMORAta project, part of my Counterforce project: https://nick-black.com/dankwiki/index.php?title=InaMORAta https://nick-black.com/dankwiki/index.php?title=InaMORAta https://nick-black.com/dankwiki/index.php?title=Counterforce https://nick-black.com/dankwiki/index.php?title=Counterforce hack on!
- aliswe 4y ago
  nothing on bladeless fans, i am curious if they are useful or useless ... i am guessing a bladeless fan has a bladed fan inside though.
  - dankamongmen 4y ago
    i know nothing about them! thanks for bringing them to my attention.
    - aliswe 4y ago
      Would be interesting to know how/if/when they are superior to bladed fans, power consumption wise I'm guessing is the only possible way.
deleted 4y ago
[deleted]

175 points by dankamongmen 4y ago

Great to know, though more of a Mac fan myself... (sorry)

Honestly this isn't more than I cared to know about PC fans. I've worked extensively with industrial appliances and fans are bloody important and underlooked: fan failure is often the step that precedes component failure. The one part of the spec I wasn't aware of was just how insanely high the maximum current draw is; I'm glad that we've made more efficient, longer-lasting, effectively silent air-movers that can fit easily within that power budget.

rietta 4y ago
Adding fans to consumer devices that don't have them but should, such as a cable modem, certainly improves its reliability in my experience!
- Eisenstein 4y ago
  The problem with that is when the fan would block the natural venting if it stops working. These devices are engineered to have the heat move the air through and out of the device, and though a fan will usually do a better job of that, it will ultimately fail. When it does, if the fan body is in the way then the intended convection is blocked and the entire unit shuts down or is damaged.
  - Retric 4y ago
    Cable modems are often placed in poorly ventilated spaces that overheat. So you can get the best of both worlds by including generally unneeded fans which enable the device to function in sub optimal conditions, but can also extend lifespan in better ventilated spaces. The alternative of passive cooling in such spaces is unreasonably expense because only a subset of devices are subjected to such conditions.
    - rietta 4y ago
      I have thought about adding a bathroom style vent fan to the closet that houses the network gear for the house. Exhaust near the top and have a cool air intake near the floor.
      - js2 4y ago
        AC Infinity make fans specifically for this purpose: https://acinfinity.com/closet-room-fan-systems/ https://acinfinity.com/closet-room-fan-systems/ Bathroom fans work too if you’re able to vent through the ceiling. I can recommend the Panasonic whisper fans (available under a variety of models with “whisper” in the name). I’m using one to exhaust the warm air from my home theater emitted by the projector. I think it’s this one: https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/retail-fans/whisper-choicetm-ventilation-fan-pick-flowtm-80-or-110-cfm https://na.panasonic.com/us/home-and-building-solutions/vent...
- post_break 4y ago
  Slow big fans on my home receiver kept it going much longer than it probably would have lasted passively cooled.
  - aidenn0 4y ago
    Can you recommend a fan setup for that?
    - post_break 4y ago
      AC Infinity usb fan on amazon. Silent, but moves enough air, and you can bump up the speed.
dankamongmen 4y ago
yeah, if you look at the equations at the bottom, power goes up with the third power in relation to rpm. whippin' and drivin' that much air takes some oomph. connect that fan to any normal motherboard, and you're going to burn out your fan header pretty much immediately (especially since inrush current is probably even higher than the steady state).
- c_o_n_v_e_x 4y ago
  For those interested, the equations are also known as fan or pump affinity laws: https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.html https://www.engineeringtoolbox.com/fan-affinity-laws-d_196.h...

magicalhippo 4y ago

What I want to know is how a ballbearing-less fan suddenly decides to go brrrrrrr. So far I've been lazy and just replacing them, but I'd be nice to know as they seem fine when I spin them manually.

hoseja 4y ago
Are you sure it's not a resonance elsewhere?
- magicalhippo 4y ago
  Yes, if I run the fan stand-alone it will start to brrrr after a short while.
HPsquared 4y ago
I'd imagine the fluid bearing gets a bit worn over time such that it's a bit "looser", i.e. doesn't hold the fan rotor as firmly in a straight/central position. Not enough movement to sense by hand, and no roughness, but enough looseness / free-play to allow a kind of resonant vibration or "wobble" when the fan is spinning faster. Edit: or maybe it's just very slightly worn, has debris in the bearing or something, such that it's out-of-round. I think it's the former though (resonance) as that kind of noise can be intermittent.
LooseMarmoset 4y ago
Those kinds of fans typically use a bronze bushing rather than a bearing. These bushings are long-lived, but eventually wear. When the bearing hole enlarges as part of the wear process, the fan rotor shaft now has additional room for lateral movement in the bearing and can oscillate in the the bearing rapidly, causing the "brrrrr" noise you hear. You can often extend the life of such bearings by adding a drop of light machine oil to the bearing (usually you have to pull off a sticker on the back of the fan to access the bearing).

bayindirh 4y ago

Nick Black's personal wiki is a treasure trove. The style is a little terse, but it's a non-issue for me.

dankamongmen 4y ago
thanks; this warmed my little hacker heart!
- bayindirh 4y ago
  You're welcome. I'm pretty glad that I found your (not so) small corner on the net, and bookmarked it. Cheers!

wallaBBB 4y ago

Depth of fan analysis in PSU reviews you could find on jonnyguru beats this by a mile. Too bad jonnyguru site is no more.

rietta 4y ago

Nick has been a prolific writer as long as I have known him. This is some great, esoteric stuff, about fans. I have used case fans in unusual applications not involving a computer but never went deeper than provide sufficient power that it spins full speed. For my own builds, I usually just plugged the fan in without a second thought.

owenversteeg 4y ago

Does anyone know if there are high-heat-resistant PC fans (and at what temperatures normal PC fans will melt)? The only fans I can find that claim to be heat-resistant are the Noctua Industrial PPC series which, aside from not being cheap at $33/piece are "only" heat-resistant up to 140C and the airflow isn't crazy high - subjectively the ones I've got feel like they move substantially less air than a standard diesel heater blower fan. Ideally I'd be interested in something that's >180C resistant but if there are any other options around say 140C max then I'd also be interested.

tinco 4y ago
If $33 is not cheap then maybe not. But I buy my delta fans at mouser or digikey, and they have a wider range of specs than typical consumer websites. They come without connectors though so there's some crimping/soldering required. For our little rendering cluster I bought a bunch of 12.000 rpm fans to cool the rack mounted threadrippers. Worked fine, no watercooling in the rack needed and 4ghz on all cores under load.
- somat 4y ago
  For some reason I got all opinionated about fans and settled on delta as my preferred brand. I think because delta actually had data sheets. The cool thing is that digikey has the exact fans I want, the downside is that the fans digikey sells have no plugs. I tried once to terminate it myself but I was too cheap to buy the correct tools, so that did not go well. and am now a bit bummed about the whole thing, I found a vendor I can trust to sell me real delta fans.. and they have no plugs. sigh will probably stick with nocturna as a good second best.
jenscow 4y ago
I prefer fans that are not heat-resistant. That way, it has more motivation to do its job properly.
- fnordpiglet 4y ago
  The melting will stop when cooling improves.

ilyt 4y ago

I'm surprised it doesn't mention hysteresis some fans have at low speed. Cheap fans often don't have actual proper speed controller on them which means they might start spinning at say 30% PWM but only stop spinning at 15% PWM. That was probably the thing that surprised me most when I upgraded to nice Noctua, at certain PWM it just started, always, and below that it stopped, always.

paxswill 4y ago
Those fans that start at 30% and then allow you to go lower are explicitly allowed by the spec from Intel (linked in the article, sec 3.2 and 3.4).
- ThePowerOfFuet 4y ago
  Allowance in the spec doesn't mean that behaviour is desirable.

antifa 4y ago

I wish noctua would sell aftermarket replacement CPU fans for laptops. I thought there was something wrong with the loudness of my Dell laptop's fan (with low confidence), but I couldn't gauge that any replacement product wound actually be quieter or cared about noise levels.

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nicolaslem 4y ago
Most laptop parts are specifically designed for a particular laptop model. This is very different from the highly standardized desktop parts. Noctua would be sure to lose money selling laptop fans.

rajup 4y ago

Ah reminds me of the time when I was a kid and my PC would randomly crash and would not start for a while. Turns out the processor fan was janky and would not start occasionally requiring a push with a pen or something to get it going. So the POST process in my case had an extra step: "have human check CPU fan"!

themoonisachees 4y ago
Same, but my motherboard actually checked the fan was spinning so post literally involved me checking the fan when told

whalesalad 4y ago

What a coincidence, 4x of the 120mm Noctua Redux fans just arrived this morning and are sitting on my living room table waiting to go into my rig. I love in-depth analysis of stuff like this. How do y'all like to manage (chassis) fan speeds? I have been out of the PC world for so long that I forget all pieces of hardware need to be managed.

ChoGGi 4y ago
I use a Corsair commander with a copy of system information viewer
- whalesalad 4y ago
  Dig the fact that this thing comes with little temperature probes - my current case is probably a little too small for the setup I have right now and I am debugging the temperature zones / airflow. It's a Fractal Define C, i7-12700K, Radeon RX 6750XT OC. Initially my CPU cooler fans (2x) were pointed in opposite directions, lol. Would love a thermal camera, but these probes would probably be just as helpful.
gregmac 4y ago
FWIW I used to use software (Speedfan, and later something else I don't remember), but after upgrading to Noctua fans, I found whatever is built-in to the motherboard works just fine and gave up on the complication of software. I'm on my second system like this, and I've found they've both been a good temperature and nearly silent most of the time. Even maxed out, it still seems to be quieter and cooler than it would be with most (cheap) fans.
- whalesalad 4y ago
  nice, that was what I was hoping to achieve
MivLives 4y ago
4 way fan splitter to just let the mobo control it all. I run mini itx so not a lot of fan headers.

Markoff 4y ago

I haven't assembled PC in long time, by now I'd expect you can build passively cooled PC if you use PC just for some regular office job and surfing without gaming and resource heavy apps or we are still not there? Back in the days undervolting was for me for interesting than overclocking to make PC as quiet as possible.

kadoban 4y ago
Some passively cooled PCs exist, but they're niche and expensive. It's a lot easier to make one that's quiet, but not silent. Big fans that spin slow and not going crazy with bleeding-edge hardware do wonders. Yeah, if you really want, you can try to underclock/undervolt some things here and there.
- wtallis 4y ago
  I think it's useful to draw a distinction between a silent computer and one that is merely inaudible. For a typical PC, all you really want is for it to not noticeably raise the noise floor of the office it occupies. Going down the route of truly silent PCs forces severe compromises, and in almost every use case it would be better to have fans, properly configured to always spin, with a minimum speed low enough to be inaudible.
scns 4y ago
It is absolutely possible, even with a high performance GPU! [0] A video review by LTT [1] [0] https://www.monsterlabo.com/ https://www.monsterlabo.com/ [1] https://www.youtube.com/watch?v=_jYB-RpkmUc https://www.youtube.com/watch?v=_jYB-RpkmUc

egberts1 4y ago

So looking forward to the incomplete "Form Factor" section!!!

axiolite 4y ago

> "there is no readily-available 24V source from an ATX power supply," This is false. ATX provides both +12V and -12V: * https://pinoutguide.com/Power/atxpower_pinout.shtml https://pinoutguide.com/Power/atxpower_pinout.shtml Hooking them together would provide 24VDC. On a 350W PSU, I see -12V rated to supply 0.3A, which would allow for 24V fans drawing up to 7.2W of power, if desirable. I don't see any reason to prefer 24V fans, however. The current losses over such short ranges are minimal, and I would think the larger economies of scale of 12V devices will keep 12V fans less expensive.

gnu8 4y ago
This led me to wonder why we still need the -12V supply - I know the -5V supply was removed a while ago because it was only needed for ISA slots. According to Wikipedia, -12V is for RS-232 ports and PCI slots, both of which are hardly seen on any current motherboards. It should be safe to use it for fans, but 7.2 watts is not very much power. Looking on Mouser, I see 24VDC fans that consume 1 watt or 18 watts depending on speed, so one could easily overload the -12V bus if they are trying to get a lot of CFM. I don’t see a compelling reason to use 24V fans in a PC.
- iknowstuff 4y ago
  I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.
  - toast0 4y ago
    From what I've read, ATX12VO really is 12V only; peripheral power connectors (sata/molex) will be connected to the motherboard, where the 5v and 3.3v (if needed) will be generated. 3.3V on sata power plugs was never reliably available and was rarely if ever used, and one of the pins was redfined to be a disable pin, so it's usually best for everyone if 3.3V isn't provided at all. -12V for RS-232 is easily generated from +5V or similar sources; max232 chips have been available since the 80s
  - 0cf8612b2e1e 4y ago

amelius 4y ago

How does a fan get power to drive the tach output, if the only power it gets is a pwm signal (which might be low when it needs to switch)?

mrWiz 4y ago
Generally the fans are powered with a steady state DC source and the PWM is just logic signaling. If the fan is powered by a PWM source the tach output will not be a clean square wave (but could still be reconstructed, if the PWM frequency is sufficiently higher frequency than the fan's rotational speed).
- amelius 4y ago
  Well, PC fans come in 3-wire and 4-wire forms, where the 3-wire type has only pwm,tach and GND connections (no DC power).
  - robotguy 4y ago
    3-wire is: TACH, DC, GND 4-wire is: PWM, TACH, DC, GND https://noctua.at/en/what-pin-configuration-do-noctua-products-use https://noctua.at/en/what-pin-configuration-do-noctua-produc...
    - amelius 4y ago
      In practice pwm is used instead of DC.
      - wtallis 4y ago
        I can't remember the last time I encountered a motherboard that didn't offer you the choice between DC voltage and PWM for fan speed control. Both are still mainstream options; CPU heatsink fans are almost always 4-pin PWM fans but case fans are very commonly 3-pin DC fans. AIO Water cooling kits also commonly use 3-pin fans, especially when integrating their own fan controller or multiplexer so that they only need to occupy one or two fan headers on the motherboard. (Edit: if you mean that in practice, the motherboard approximates DC voltage control using a PWM-based method, that may be true, but it's beside the point; a 3-pin fan is missing the control circuitry that a 4-pin PWM fan uses, and the 3-pin fan's behaviors like turn-on point will be specified in terms of DC voltage not PWM duty cycle, and you can't drive a 3-pin fan with the PWM signal intended for a 4-pin fan because the voltage and current supplied are both far too low.)

deathanatos 4y ago

The pinout is wrong, is it not? As it is drawn, if you mate the two connectors, the wires won't match up. (You'll need to mentally rotate it: the hook on the back of the male connector slots into the rails on the front of the female connector to make them impossible to separate without destroying a nail.) I think the female side is right, it's the male connector that's reversed.

pwg 4y ago
> The pinout is wrong, is it not? Not if both connectors are drawn looking top-down. Note the ribbing and clip on the female connector, the bottom of the female connector is at the bottom of the drawing. You'd mate these by lifting the female straight up, rotating about 90 degrees along the vertical axis, and pushing down onto the male connector. And when mated that way, the labeled pin-outs line up perfectly.
- deathanatos 4y ago
  Oh, you're right; it's drawn such that the business end's holes for the pins are hidden on the bottom; the wires should be coming out the top, but they're not rendered. (So, the pinout is right.) (Edit: in my defense, the CAD model's square holes on that end are pin holes, not wire holes, which would almost certainly be wider, not square, and take up more of the space available on that side, and do on the connector I have. Hard to find a photo on Google, as nobody photographs the non-business-end…)

deathanatos 4y ago

Also, one thing I've always wondered: why do people want to use hwmon to set fan RPMs? (Or really, why do this from userspace at all?) It seems inherently dangerous to me, as you're asking a process who might not receive CPU time for whatever reasons from the very much not realtime OS to control a fan; if the current RPM is too low, and the system starts generating heat, but the fan controlling process doesn't get CPU time … then what happens? It seems to me you want fans controlled with something dedicated to it. The other thing I don't get is all the plethora of options my motherboard gives me to set fans only to fixed RPMs. Am I crazy in that I want the fan to be controlled by heat? (More heat => more RPMs. Keep the system cool, but if there isn't much thermal load, spin the fans down and reduce the noise?) But by fixing an RPM, it seems the only valid input is "100%"; anything else could be too low under stressful conditions. I could also have a cheap motherboard. (I definitely won't be purchasing from this manufacturer again, and the motherboard does have other severe quality issues…)

MaulingMonkey 4y ago
> It seems inherently dangerous to me In the old days, it kinda was - at least to your hardware. Then people realized that blowing up components because a fan failed, or became unplugged, or a filter clogged with dust, maybe wasn't a great user experience and/or caused more in-warranty returns that required replacing hardware ($$expensive$$!), and implemented thermal throttling and thermal cutoffs. Nearly two decades ago at this point, I helped a friend diagnose his computer randomly turning off. It turned out to be a CPU fan unplugged itself, causing overheating to trigger a thermal cutoff. No other apparent harm done. Fans aren't the only means of limiting heat: slowing stuff down and turning stuff off also works. And it turns out users sometimes would rather stuff run slow than run loud, and maybe your crappy motherboard vendor shouldn't be writing a ton of code running in kernel space - with all the potential stability and security issues that might entail - for whatever network-connected bloatware syncs your RGB lighting and fan settings to the cloud. And they will do exactly that, if that's what's required to give their customers what they want. Just exposing fan RPMs to userspace might be far less dangerous.
- deathanatos 4y ago

zajio1am 4y ago

One sad thing with fans in PC is how bad is fan controller / SuperIO driver support in Linux. AFAIK, there is no autodetection for SuperIO chips (like there is for PCI or USB devices) and for many chips there are no drivers anyways. Seems like using USB connected microcontroller with open-source firmware instead of embedded SuperIO seems like easiest way to have reliable fan control in PC.

fiat_fandango 4y ago

Just when we thought Linus Tech Tips had exhausted every normie, low effort way to "investigate" which fan is best to cool a consumer CPU and GPU for gaming...

dankamongmen 4y ago
not at all what i was trying to investigate, but thanks

tristor 4y ago

This was a great read, I have always had a love of PC fans, and the technology behind them. It'd quite a complicated engineering challenge to produce a high static pressure, high rate of airflow, and minimize noise while maintaining high reliability. I'm one of those folks that has no problem dropping significant money on fans every time I do a PC build, and so far I have very very rarely ever had a fan fail on me, even after decades of running at high duty cycles. The thing I always marvel at is how high the draw is for some of these fans. At one point I even retrofitted a system with an external radiator for water cooling that used 120V 120mm Panaflos and was separately powered from the computer. I wish folks took cooling more seriously. There are so many devices that benefit from active cooling but rarely get it, or even being strategic around placement, positioning, and mounting to make convective cooling more effective. Thermal limiting is such a common occurrence on modern electronics if you don't give due consideration to cooling, as we've moved towards more passively cooled devices, including PCs (laptop especially).

rkagerer 4y ago

This is great. I determined some time back the most important thing I need to know is "buy Noctua". They're expensive but have consistently outlived all other PC fans I've ever tried.

Scene_Cast2 4y ago

One interesting thing to note is the P/Q fan curve. It plots how much air a fan, at a specific PWM frequency, moves against a variable restriction (measured in pressure drop). Here's a sample - https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-f12-and-nf-s12a https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-... Hypothetically, knowing the heatsink airflow curve, one can find the amount of air a fan will move across. There are PQ curves (either reported or measured) for a bunch of fans and some radiators out there.

dankamongmen 4y ago

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aliswe 4y ago
nothing on bladeless fans, i am curious if they are useful or useless ... i am guessing a bladeless fan has a bladed fan inside though.
- dankamongmen 4y ago
  i know nothing about them! thanks for bringing them to my attention.
  - aliswe 4y ago
    Would be interesting to know how/if/when they are superior to bladed fans, power consumption wise I'm guessing is the only possible way.

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