Question 140mm case fan slow to start-up upon powering on computer after BIOS update and 3700X installation

CooLWoLF

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May 15, 2009
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Having a very strange issue. I updated my ASRock x370 Killer SLI to bios version 6.0 today and installed a new Ryzen 3700X CPU. After the updates, now one of my 140mm front case fans lags on start-up when first powering on the computer. I have 2 of the same fan in the front panel (Thermaltake Riing 140mm). The fans are each plugged into a motherboard fan header. One of the fans starts up immediately upon hitting the power button as normal, but the other lags about 3-4 seconds before it starts spinning or lights up. Any ideas? I am totally perplexed.
 

CooLWoLF

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Update: I re-connected the fan to a molex adapter, so direct power from the power supply. Now the fan works as normal again, so its definitely something wrong or buggy with the motherboard/fan header.
 
Update: I re-connected the fan to a molex adapter, so direct power from the power supply. Now the fan works as normal again, so its definitely something wrong or buggy with the motherboard/fan header.
It's now running full speed all the time so that's not ideal.
Connect it back to appropriate header on the MB, and in BIOS set as DC control or PWM (depending on if it's 3 or 4 pin) and set it's speed curve same as the other one.
Fan speed is governed by a temperature sensor of the header it's connected to and it's probably waiting for temperature to raise enough for it to start.
 
Oct 7, 2020
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It's now running full speed all the time so that's not ideal.
Connect it back to appropriate header on the MB, and in BIOS set as DC control or PWM (depending on if it's 3 or 4 pin) and set it's speed curve same as the other one.
Fan speed is governed by a temperature sensor of the header it's connected to and it's probably waiting for temperature to raise enough for it to start.
It was nice of you to try to help but it would've been nicer if you gave a little more attention to detail. The OP stated at least once that the fan was not just slow, that it was lagging 3 to 4 seconds. I don't recall any bios setting that has the fan do that, and if there is one it should be removed.
 
It was nice of you to try to help but it would've been nicer if you gave a little more attention to detail. The OP stated at least once that the fan was not just slow, that it was lagging 3 to 4 seconds. I don't recall any bios setting that has the fan do that, and if there is one it should be removed.
I've seen that but reason could be same, adjusting curve at which temp and voltage it starts is cure.
 

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