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More than you cared to know about PC fans

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Re: More than you cared to know about PC fans

#61

Post by deathanatos »

pwg wrote: post #49
deathanatos wrote: post #44

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.

> 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.

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…)

Re: More than you cared to know about PC fans

#63

Post by iknowstuff »

gnu8 wrote: post #41
axiolite wrote: post #34

> "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 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 s…

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 dependi…

I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.

Re: More than you cared to know about PC fans

#64

Post by LorenPechtel »

MaulingMonkey wrote: post #48
deathanatos wrote: post #46

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 CP…

> 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…

Yup, I got random thermal shutoffs. The pump in the water cooling loop had failed.

Re: More than you cared to know about PC fans

#65

Post by wtallis »

deathanatos wrote: post #60
MaulingMonkey wrote: post #48

Earlier quoted context omitted.

> 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…

> 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 This wasn't the suggestion I was making. I was suggesting that the motherboard, itself , should be controlling the fan RPMs (or should at least provide such a mode). I don't feel like taking a temperature input, and mapping that to an RPM output…

On typical desktop motherboards, the Super IO chip handles all the temperature monitoring and fan control. Those chips usually have a few modes to configure some very simple control system for mapping temperature inputs to fan speed outputs (never anything as advanced as a PID controller).

The main problem is that the Super IO only has access to the temperature sensors on the motherboard itself, and on the CPU (these days, through PECI). There's no standard way for the Super IO to do out of band monitoring of temperatures on your GPU or storage drives, so if you want those to affect fan speeds you need to implement it in software.

Servers typically have BMCs controlling fans, and even Apple's x86 machines have their SMC; in both cases you typically see a more thorough monitoring of component temperatures, configured out of the box with a proper awareness of which fans are blowing across which components. But that stuff doesn't trickle down to the build your own desktop market.

Re: More than you cared to know about PC fans

#66

Post by toast0 »

iknowstuff wrote: post #63
gnu8 wrote: post #41

Earlier quoted context omitted.

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 dependi…

I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.

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

Re: More than you cared to know about PC fans

#67

Post by toast0 »

deathanatos wrote: post #46

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 CP…

> why do people want to use hwmon to set fan RPMs? (Or really, why do this from userspace at all?)

Some people want to have a mode switch; normal use should be silent/quiet, but when you know you're going to do something big (game, big compile, etc), fix the fans at full so the noise is consistent and cooling is best. (the cooler the chip, the more the boost)

Some people have no good options from the system firmware, and getting _something_ configurable is better. I've run on systems where I couldn't tell the system to actually run the fan, so things would get hot and throttle. Userspace configurability is better than nothing. This tends to be a bigger issue on things that are sold as a whole computer, like laptops, and small formfactor things (which are often pretty much laptops without a battery and built in user interface devices) but also some name brand desktops.

My recent motherboards all seem to have a pretty nice fan configuration tool. Presets for quiet/performance/full speed, and a simple graph based UI to set % by temperature. Most of the fan headers can be set to follow the cpu temperature or the system temperature. When you buy the nice Noctua fans, they also ship 'low noise adapters' that I assume drop the voltage and limit the maximum RPMs and limit noise. Depending on your overall cooling design, that can be reasonable or asking for trouble.

Re: More than you cared to know about PC fans

#68

Post by aidenn0 »

post_break wrote: post #57
rietta wrote: post #10

Earlier quoted context omitted.

Adding fans to consumer devices that don't have them but should, such as a cable modem, certainly improves its reliability in my experience!

Slow big fans on my home receiver kept it going much longer than it probably would have lasted passively cooled.

Can you recommend a fan setup for that?

Re: More than you cared to know about PC fans

#69

Post by 0cf8612b2e1e »

iknowstuff wrote: post #63
gnu8 wrote: post #41

Earlier quoted context omitted.

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 dependi…

I think the ATX12VO standard might be getting rid of -12V. All it does is 12V.

Any chance they are going to add something higher? 19v would align with laptops and make power hungry GPUs slightly more manageable.

Re: More than you cared to know about PC fans

#70

Post by MaulingMonkey »

deathanatos wrote: post #60
MaulingMonkey wrote: post #48

Earlier quoted context omitted.

> 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…

> 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 This wasn't the suggestion I was making. I was suggesting that the motherboard, itself , should be controlling the fan RPMs (or should at least provide such a mode). I don't feel like taking a temperature input, and mapping that to an RPM output…

> I was thinking a (very small) auxiliary chip, dedicated to the task.

Extra cost (both in design and manufacture), new potential point of failure (both for manufacture and in the field), when the CPU failing was already a single point of failure for the machine. It's not that a full-blown CPU is required, it's that you already have a full-blown CPU that can do the job, simplifying the design. Well, you might see dedicated fan control hardware for server motherboards and other more industrial focused applications, but they often need to coordinate pumps/fans for an entire building - reliability in this context is more about redundancy, and alerting maintainence to the need for repairs, or perhaps switching to a new primary datacenter if the failure is big enough - not in attempting the impossible of ensuring 100% reliability for any individual component.

> CPU death spirals

Have you actually seen one of these that noticably bogs down the fan-driving firmware/drivers and causing issues? I haven't. I've had fan failures. I've had plenty of hardware controlled fans go full apeshit 100% power to the point of being not merely a nuisance, but a problem (audio, vibration, wear+tear, ...). I've heard of building cooling failures. But I don't think I've seen so much as a blog post about the CPU getting so starved that it can't spin up the CPU fans.

And I've had fans not working hard enough - but I'd rather flip a setting in software than open up a case and go hunting for the right jumper, typically. Less disruptive - and the machine is typically usable enough I can still download/install missing software, and google appropriate documentation, which is frequently a lot more difficult to do with the case open.

---

I guess my main point here is that reliable hardware must already assume the potential for cooling failures, and that extra hardware or engineering for a minor improvement to a "purely theoretical" failure mode doesn't sound like it'd pay for itself.

100% have hardware temperature throttles and cutoffs though. Those cut in for a lot of very real failure modes, that I've only heard of actually happening, but personally experienced. Those will pay for themselves.

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