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CPU_OPT header Motherboard Detection

Jesseinsf
Level 10

‎05-21-2020 06:26 PM - last edited on ‎03-05-2024 08:02 PM by Community Admin

Today I just added a fan to the CPU_OPT header. When I checked the monitoring section of the BIOS it doesn't detect the fan and says "NA", but the fan is on and working. Same goes for AI Suite 3. However if I change the fan speed of just the CPU Fan then it also controls CPU_OPT. Is this normal or is there a malfunction? If this is an issue, then would anyone know a solution? I just like things to work as advertised.
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pndiode
Level 11

‎05-21-2020 08:20 PM

CPU_OPT is slave to CPU_FAN.
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Jesseinsf
Level 10
In response to pndiode

‎05-21-2020 08:31 PM

pndiode wrote:
CPU_OPT is slave to CPU_FAN.

So the entry in the BIOS for my MB should be disregarded? One would think that if the Monitoring section in the BIOS has a CPU_OPT listed that the BIOS would detect it. I only want to see the fan speed. I'm thinking that the sensor in the fan is not working. I am getting more fans next week which I will test my theory.
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pndiode
Level 11
In response to Jesseinsf

‎05-21-2020 09:31 PM

Jesseinsf wrote:
So the entry in the BIOS for my MB should be disregarded? One would think that if the Monitoring section in the BIOS has a CPU_OPT listed that the BIOS would detect it. I only want to see the fan speed. I'm thinking that the sensor in the fan is not working. I am getting more fans next week which I will test my theory.


Okay, now I understand, but I do not have that motherboard. No, the CPU Optional Fan speed should register in BIOS when a fan is connected to the CPU_OPT. I tried it with a 3-pin and 4-pin fan, both show speed in rpm. The only time it shows N/A is when no fan is connected (VIII Gene/Formula, IX Extreme does not have CPU_OPT).
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Jesseinsf
Level 10
In response to pndiode

‎05-22-2020 08:18 PM

pndiode wrote:
Okay, now I understand, but I do not have that motherboard. No, the CPU Optional Fan speed should register in BIOS when a fan is connected to the CPU_OPT. I tried it with a 3-pin and 4-pin fan, both show speed in rpm. The only time it shows N/A is when no fan is connected (VIII Gene/Formula, IX Extreme does not have CPU_OPT).

I figured it out. You can't have 2 fans connected to the CPU_FAN header if you want the motherboard to detect the fan speed from the fan connected to the CPU_OPT header (One fan per CPU header). If you have an 360mm AIO then one of the fans needs to be connected to another header like a Radiator header.
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