Hello everyone

Problem: The CaseFan hardware CHA_FAN2 does not properly enumerate when mains power isfirst applied, but works on subsequent boots as long as mains powerstays connected.

Config: H170M Pro4with v2.0 BIOS, Silverstone ST50F-ESG 500W power supply, Windows 10Home 64-bit, Intel Core i5-6600 CPU stock fan, Noctua 80mm NF-R8Redux Edition PWM Case Fans

Consider thisprocedure:

1. Power isdisconnected from the power supply
2. Power cord isplugged in, and the PC turned on
3. Themotherboard does a configuration scan (POST maybe?); all fans spinmomentarily (CHA_FAN1, CHA_FAN2, CPU_FAN1). This appears to take awhile.
4. Motherboard(eventually) starts, ASrock splash screen shows, and the OS beginsto boot, where now only one case fan and CPU fan are spinning(CHA_FAN1, CPU_FAN1)
5. CHA_FAN2never spins, and using a tool like HWiNFO to interrogate thehardware, it shows thisfan's hardware ismissing completely (notjust 0 RPM)
6. Shutdown theOS; but leave power cord connected to the supply
7. Turn on thePC again; the motherboard starts much faster than earlier and thistime the fan will spin up & appear in the HWiNFO tool withcurrent speed
8. Fan willoperate normally after every shutdown or reboot as long as poweris not removed from the power supply. The fan goes missingagain on first boot if power is disconnected.

I contacted techsupport on this problem, but they said they were unable to reproduceit. So I'm putting out the question to others to see if they havethe same issue. Here is what tech support said to try:

• Load BIOSdefault settings
• Test thechassis Fan which installed at CHA_FAN2 to other fan header, oranother fan to this header
• In H/WMonitor tab, please set the CHA_FAN2 to "Full Speed"

I haven't triedany of these as the PC now belongs to a family member some distanceaway, but since the fan does actually work the diagnostic steps seemredundant to me anyway.

I hope someone canreproduce this, so I can take it back to Asrock for analysis.

Thank for reading!