Question Help setting up (AIO) fan modes in the BIOS ?

[abyss010]

I have a Corsair H100 AIO and some standard Arctic fans. My motherboard is an MSI Z490

Would anyone be able to advise which modes to set my fans? I am mostly puzzled about my AIO. I can't find much information on this model as it seems most people have the newer ones.

The CPU temperatures are very good, around 38-40c idle (im guessing summer plays a factor) and 65c while gaming but I never actually changed these settings until getting this new AIO, so I would like to confirm it's right as to avoid any damage. I've never had a liquid cooler before.

Currently I have CPU_FAN set to PWM mode and all SYS_FAN set to DC.


CPU_FAN was automatically set to Auto/DC so I changed it to PWM.
Reverting CPU_FAN to DC seems to go right down to 0RPM with no movement, but PWM makes it run at around 3000PM. Is this correct?

Changing some of the other SYS_FANs to PWM results in higher RPM and louder PC. One of the RPM falls lower if changed from DC to PWM (maybe this is the AIO fan, I need to check which one its plugged into).

I have the Corsair pump in CPU_FAN (as instructed) and it's fans in a SYS_FAN header, other case fans are also in SYS_FAN headers.

I believe the pump is 3-pin.

I have "CPU Cooler Tuning" in MSI BIOS set to Water Cooler.

Also, it says "Do not utilize voltage fan control on the CPU_FAN header with the pump connected for the best performance experience." in the AIO online manual but I'm not technically literate enough to understand, so would appreciate an explanation.

Really, I could just be overthinking but hearing some perspective is good

 

[Paperdoc]

Your mobo manual on p. 61 shows the typical screen for fan header adjustments. At upper right you choose one header at a time to make any changes.

General rule: for any fan with FOUR wires in its cable and ending in a fan connector with FOUR holes, the header it is plugged into should always be set to PWM. Normally for an older 3-pin fan the header should be set to Voltage to DC. BUT the PUMP in an AIO system is special! Its header ALSO should be set to PWM as the Corsair H100 manual says. This uses a quirk of the fan systems to ensure that the pump always runs full speed as designed. The 3000 RPM reading you report sounds right. So you should change this setting for your SYS_FAN headers since all of your fans, I suspect, are the 4-pin type.

Here's another item to adjust. You have the RAD FANS of the H100 system connected to one SYS_FAN header using a small Splitter supplied with them. On the screen for that particular header, note the item at left centre for Temperature Source. Set this to CPU for the rad cooler fans. Set it to Motherboard for all your case vent fan headers. That way the Rad Fans' speeds will be automatically adjusted according to the temperature inside the CPU chip, but he case vent fans' speeds will be adjusted according to a different sensor on the motherboard.

When you have adjusted all your fan headers, use Esc back to Main Menu, then F10 to pop up a confirmation screen. Confirm that it should SAVE your new settings and reboot.

 

[abyss010]

Your mobo manual on p. 61 shows the typical screen for fan header adjustments. At upper right you choose one header at a time to make any changes.

General rule: for any fan with FOUR wires in its cable and ending in a fan connector with FOUR holes, the header it is plugged into should always be set to PWM. Normally for an older 3-pin fan the header should be set to Voltage to DC. BUT the PUMP in an AIO system is special! Its header ALSO should be set to PWM as the Corsair H100 manual says. This uses a quirk of the fan systems to ensure that the pump always runs full speed as designed. The 3000 RPM reading you report sounds right. So you should change this setting for your SYS_FAN headers since all of your fans, I suspect, are the 4-pin type.

Here's another item to adjust. You have the RAD FANS of the H100 system connected to one SYS_FAN header using a small Splitter supplied with them. On the screen for that particular header, note the item at left centre for Temperature Source. Set this to CPU for the rad cooler fans. Set it to Motherboard for all your case vent fan headers. That way the Rad Fans' speeds will be automatically adjusted according to the temperature inside the CPU chip, but he case vent fans' speeds will be adjusted according to a different sensor on the motherboard.

When you have adjusted all your fan headers, use Esc back to Main Menu, then F10 to pop up a confirmation screen. Confirm that it should SAVE your new settings and reboot.

Thanks for the help, I changed my case fans to PWM and set the source to System. There isn't a Motherboard option but I assume it is the same thing.

I still have the RAD fans on DC as it lowers on PWM, should I change this?

Should I also enable smart fan mode on the case fans and/or the RAD Fans or leave it as is?

 

[Paperdoc]

Enabling Smart Fan Mode for all headers is OK, perhaps the best choice. BUT you WILL need to check one thing particularly. For EVERY header after you have made this change, check the MODE setting at upper left. Again, ALL should be set to PWM, including the CPU_FAN where the pump is connected. That assumes that all your fans are the newer 4-pin PWM type.

Older 3-pin fans and newer 4-pin fans are designed differently but with as much compatibility as possible for easing their introduction into the marketplace years ago. Among these, the new 4-pin fans were designed to be able to work when given the older type of signals. BUT that is not ideal for them. They really should be fed from PWM signal systems. So for any 4-pin modern fan its header should be set to PWM Mode. One advantage of this is that the fan can be operated at a lower minimum speed without risking stalling. Plus, with that system the fan CAN operate properly over the entire range of speed settings.

For the case fans on the SYS_FAN headers you are right to select the System option for Temperature Source.

 

[abyss010]

Thank you so much again, I'm glad that everything is sorted. I'm also getting lower temps now.

One thing though, I'm curious as to why switching to PWM and enabling smart fan mode on the RAD fan drops the speed from 1000RPM to 850RPM.

Assuming the RAD fan is the two RGB fans on top (hence the radiator fans).

 

[Paperdoc]

This gets into the esoteric details of how fan speeds are managed. Although we all talk glibly about Fan Speed Control, the truth is that it REALLY is TEMPERATURE Control. That is, the target is a TEMPERATURE, and the automatic system manipulates the signal it sends out to a fan to set its speed. In fact it does NOT care what that speed is. Even though it gets a speed signal from the fan and can show that to you, it does NOT use that info for any of this! If temperature rises it increases the signal sent out, and vice versa.

The basic strategy is called "feed-forward" control. That is, for EACH header - let's talk only about the CPU_FAN header, but others work the same way - it has a PROFILE or strategy that looks at the actual temperature reported by the relevant sensor and from that predicts what the fan speed signal should be to keep that temp from going higher. The prediction is based solely on a Fan Curve of output versus temp, and it has one pre-set curve in BIOS. (Most systems allow you to tell it to use instead a curve you set yourself .) The signal sent out is basically a "% of Full Speed" signal because the max speed of any given fan could be quite different from others. This is a very simplistic form of control strategy. If the measured temp stays stable then the output is kept that way. If temp changes, output changes to counteract that.

The header MODE setting is the type of signal sent out to accomplish what the Profile system decided should be done. For older three-pin fans the ONLY way to set their speed is to vary the VOLTAGE sent out on Pin #2 of the header, from +12 VDC for full speed down to about +5 VDC for minimum speed without stalling. Newer 4-pin fans work differently. They ALWAYS get a fixed 12 VDC power supply from Pin #2. But that fan also has a chip inside that uses the special PWM signal from Pin #4 to modify the flow of current from Pin #2 through the motor windings to achieve speed changes. One of the backwards-compatibility features of these 4-pin fans is that, if you plug them into a header sending out older Voltage Control Mode signals, it still WILL work WITH its speed controlled. That is because it gets no PWM signal so the chip can't modify current flow, but its power supply from Pin #2 is VARYING, not fixed at +12 VDC.

What you have observed comparing the performance of the rad fans under the two MODE settings indicates that the way the header sends out signals for a particular "% of Full Speed" setting actually produces a different speed, depending on whether it is sending a reduced Voltage or a full Voltage plus PWM control signal. Remember that this system does NOT actually check what the real speed is, so it does not know about this difference.

By the way, that speed measurement by the header IS used for a second important function. It is monitored for NO signal (or in some cases, a speed below a set minimum) which it would interpret to indicate fan FAILURE. That event would cause a warning message to pop up on your screen so you can decide what to do. In the particular case of the CPU_FAN header it may even shut down your system completely in a short time without even waiting for the temperature sensor to report high temps. This is to prevent catastrophic damage to the expensive CPU caused by rapid temperture rise to beyond the chip's limit.