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.
> "there is no readily-available 24V source from an ATX power supply,"<p>This is false. ATX provides both +12V and -12V:
* <a href="https://pinoutguide.com/Power/atxpower_pinout.shtml" rel="nofollow">https://pinoutguide.com/Power/atxpower_pinout.shtml</a><p>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.<p>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.
I'm surprised it doesn't mention hysteresis some fans have at low speed.<p>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.
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.
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.<p>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).
Also, one thing I've always wondered: why do people <i>want</i> 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?<p>It seems to me you want fans controlled with something dedicated to it.<p>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?)<p>But by fixing an RPM, it seems the only valid input is "100%"; anything else could be too low under stressful conditions.<p>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…)
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.)<p>I think the female side is right, it's the male connector that's reversed.
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.<p>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.
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.
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.<p>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.
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"!
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.<p>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.
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 - <a href="https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-f12-and-nf-s12a" rel="nofollow">https://noctua.at/en/nf-a12x25-performance-comparison-to-nf-...</a><p>Hypothetically, knowing the heatsink airflow curve, one can find the amount of air a fan will move across.<p>There are PQ curves (either reported or measured) for a bunch of fans and some radiators out there.
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.
What I want to know is how a ballbearing-less fan suddenly decides to go brrrrrrr.<p>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.
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.
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:<p><a href="https://nick-black.com/dankwiki/index.php?title=InaMORAta" rel="nofollow">https://nick-black.com/dankwiki/index.php?title=InaMORAta</a>
<a href="https://nick-black.com/dankwiki/index.php?title=Counterforce" rel="nofollow">https://nick-black.com/dankwiki/index.php?title=Counterforce</a><p>hack on!
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...