Problems with PWM fan and BIOS update asrock z370

jacaru

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Dec 16, 2004
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I just setup a system using Asrock Z370 M-ITX ac motherboard. With it, I got a couple of chassis FANS, both arctic F12 & F14 PWM PST. The F12 is set at the back of the case and functions properly. But F14, in front, does not. And I already went through a replacement of the fan with no change.

The fan spins on post but then stops immediately. In BIOS, is not explicitly described as a PWM fan as the F12. The default fan profile is 'silent' and as mentioned does not spin. Changing it to 'standard' or 'performance' does not make the fan spin either. Changing it to full speed results in the fan spinning at its rated full speed, ~1300 RPM. Then changing it back to 'performance' reduces its speed to ~900 RPM, and back to 'standard' to ~400 RPM. Back to 'silent' stops. If I set my custom profile, with different RPM ratings on different temps, it wont change anything. If it is stopped it will remain stopped, if it is spinning it will spin at the same rate, whatever the power rating I set for the current temp. If anything, seems to be operating in DC mode.

In comparison, the F12 is explicitly stated as PWM. It starts spinning at post with a configured 10% power rating at ~200 RPM and changes its speed with temps following my custom profile. I would expect the F14 to behave somewhat similar. The motherboard should support this second PWM fan and it's plugged to 4 pins.

So being the second fan replacement, I tried to update the BIOS (v1.20 to v1.60), which I cant either. Tried all three methods:

a. Triggered the update from windows, exec download as admin, which ask to reboot computer. On boot, a progress bar appears that is stuck to 0% all the time.
b. Tried the USB update. Download, open archive, copy contents to FAT32 USB, plugged in USB2 back slot, boot to bios, try update. But the bios cannot find usb with update files.
c. Tried the download option directly from BIOS. Downloads update, prompts to reboot to update, but boots to the SO with nothing happening at all.

Any ideas? Thanks.



 
Solution


That means that Fan 2 header is most likely so called 'fake PWM'. While it has 4 pins, it still offers only DC control. I would swap F12 with F14 and if the problem moves to F12, then it's...
Check in BIOS if the header to which F14 is connected is set to PWM (Hardware Health Event Monitoring Screen>Chassis Fan X Control Mode where X is 1 for header next to CPU and 2 for header on right side of board), because indeed the fan shows all symptoms of being operated in DC mode.
 

jacaru

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For Chassis Fan 1, there is a control mode setting that can be set either to DC or PWM. For Chassis Fan 2, there is no such setting. In the BIOS manual is the same, describes a control mode setting for chassis fan 1 but not for chassis fan 2.

 


That means that Fan 2 header is most likely so called 'fake PWM'. While it has 4 pins, it still offers only DC control. I would swap F12 with F14 and if the problem moves to F12, then it's confirmation.
In such situation I would buy a PWM splitter and connect both fans to Fan1 header.
 
Solution

jacaru

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Thanks for the insight. Actually the PST on the fans stands for PMW sharing technology?, they come with the splitter integrated. I might do that. Although I have found some flexible control for the F14 in the 70%-100% power range that it might actually suit me. In 'standard' profile, it stops under 50C, above that I can control something between 900-1300 RPM. As I want to run silent it might be ok.