Hi! I'm wondering if setting up my fan speed in MSI Afterburner is something bad? What about if I set it up to the max? Is it dangerous? Also, I would like to know, what voltage and power control is for? If I'm not planning on oc, I should not worry about that? I've been asking stupid questions lately, is just that this is my first pc gaming, and is expensive, so I don't want to damage something. xD Thank you! Is modifying your card's behavior via MSI something bad? No. It certainly can be something bad if you don't thoroughly research before OC'ing. OC'ing is a subtle increase of a card's performance level. Let's say my card's core clock is 1380MHz. That's too low. I change it to 2000MHz because I have a weak GFX card. I go to play a game and the PC crashes. I then do a bit of research and discover changes are usually done in 25-50MHz increments. Small steps Ellie, small steps. The same applies to the memory clock. Some will be a bit more aggressive with the memory clock OC'ing. Voltage is something you should change as a very last resort. You have OC'd your GFX card and your FPS increased some but not enough for your needs. You then look to MSI AB and see voltage. 25 is also the magic number for voltage increase. 25mV increases are the norm for voltage increase. That's .025V. But now that I've OC'd and increased my voltage my card's running hot. I click on the gear(settings) in MSI AB and click on the Fan tab and enable User Defined Fan Control. Changing it to the "max" is also known as 100%. That's not really a thing. Because there are 4(or more if the user adds them) point( THERE ARE FOUR LIGHTS!!!!! ) dots in the graph which is known as the fan curve. One would have to change all of them to 100% and that isn't usually done(read never). I can set my fan to let's say 50% when the card reaches 30C, But then I don't make a significant change until it reaches 65C(which isn't normal for my card). I could change all four of those to 100% but it would be VERY loud. Dangerous? No. Will running your GFX card at 100% all the time shorten its life? Yes. How much? Idk. It's about finding that balance between noise and cooling. My card uses about 145W at full power. I can allow the card to draw more power if it needs it by setting the limit to 110%. People look to boosting the limit before increasing the voltage. https://www.youtube.com/watch?v=UH4MU-ZKP1A is a VERY informative video. It's only thirty minutes but the OC procedure described will take much longer for those not acquainted with OCing. Sure it's for the 970 and 980 but the procedures(such as the aforementioned voltage bumps) in the video can be applied to any GFX card. There are many other videos and articles that can help the user to OC most any GFX card out there. Crashing is a normal part of OC'ing. The PC will usually recover from a GFX card crash. If not, then a reset will work. That is your GFX card telling you that you have exceeded your OC limit. My card crashed so I backed of the core clock 10Hz and it was fine after that. I found my OC wall. Go past that and a crash is to be expected. If you don't OC then you shouldn't worry about fan control unless the noise is too much for you. You also have to be aware of your temperatures. Turn down the fan too much and your card can quickly overheat and that is a bad thing.

OK, just took the plunge and re-wired the fan from 12V to 5V.

To my surprise it did start no problem, and is going quite strong with more than sufficient torque - unlike another fan (non-PWM 120mm PSU fan), which doesn't start even at 7V by itself and the torque is very faint when eventually started manually.

Here are the actual experimental results:

Nominal 12V supply. RPM range was, as observed from the fan sensor wire monitoring: 1000-2500.

When modded to 5V, the RPM range got down to: 325-780. Not quite what I was hoping for (I'd be happier with at least 1k RPM at the top end), but still acceptable, at least for the winter time and especially considering the tremendously reduced fan noise level.

Note: the fan used is the Intel stock CPU HSF.

A three-pin fan connector does not include the ability to control speed dynamically, since it lacks the appropriate PWM control logic in the fan itself. PWM fans require explicit support from both the motherboard and fan itself.

If you wish to slow your CPU fan down, you can install a resistor along the the power wire (+12V) in the fan. Alternatively, you can purchase a LNA (low-noise adapter), which is essentially the same thing (although it saves you soldering in a resistor yourself). Due to the tachometer sensor discussed in the next section, you cannot put the resistor on the ground wire. You could also install a hardware fan controller (which is also essentially a resistor, albeit a variable one called a potentiometer).

If you're interested in determining how to slow your fan down with a resistor (it's honestly pretty easy), I have provided calculations at the bottom of this answer. Alternatively, you could use a potentiometer (and use these calculations to provide a rough estimate of the range of resistance needed).

If you do choose to slow your fan down (usually for noise purposes), do ensure that your load temperatures do not get too hot. Slowing down your fan will lower the efficiency of your heatsink's ability to dissipate heat... This is the classical noise versus heat debate all over.

---

For those wondering why a fan with no speed control even has three wires, the third wire is used as a tachometer output signal. Since it is tied to the same power rail as the motherboard, there is no need for an additional ground wire. According to the fan specifications I linked to above, the standard is to provide two "pulses" per revolution. The motherboard (and your hardware monitoring software) can then infer the speed of the fan from the rate of these voltage "pulses".

(I say "pulses" because the tachometer pin is pulled high by the motherboard, and every time it is "pulsed", the fan pulls the pin to ground, or 0V - and this is why you can't put a resistor on the ground wire if you want to slow the fan down).

---

To calculate the resistor you need (to put in series with the +12V wire), first determine the fan's voltage and power draw (usually listed on the fan itself). Let's assume the the fan runs on +12V, and draws 1W, and we want to slow it down to 75% of the original speed (or, drop the power down to 0.75W).

The original internal resistance of the fan is given by R = V²/P (a variation of Ohm's law and Joule's laws), and the new resistance we need will be R = V²/(0.75P). Thus, we need a resistor of size:

Rnew = V²/(0.75P) - V²/P = V²[(1/0.75P) - (1/P)].

Plugging in our numbers, we get Rnew = 12V²[(1/0.75W) - (1/1W)] = 48 Ohms. Thus, you would need to put a 48 Ohm resistor in series with the +12V fan supply to slow it down by 75% (assuming it originally draws 1W). If you have a soldering iron and some heatshrink/electrical tape handy, the resistor should cost you no more then $0.15 - just make sure the resistor is rated to at least 0.75W (preferably 1W).

Computer fans increase load current with voltage above the start threshold.

Most PC fans are <= 5W so I suspect you have an error in the decimal place.

from the red graph line I expect your case fan is identical to this with 450mA at 12V and 300mA at 9V