Question "Ultra USB Power" ports causing fans to spin after shutdown ?

[amerkiller]

Hi, bit of a weird one.
Just got a new PC with the Asrock X870 Riptide WiFi motherboard.
I use several external harddrives that are connected to a powered USB hub. The issue is as follows:

• if I connect the powered USB hub to one of the 2 ports that are labelled as "Ultra USB Power" and then turn off my PC, within a second of turning off all the case fans start spinning again, at max speed. All the other RGB and fans (e.g. CPU or GPU fans) are off, it's just the case fans that start spinning.
• if I connect the powered USB hub to a different usb port, one that is NOT labelled "Ultra USB Power", everything is as expected - I turn the PC off and no fans are spinning, the PC is "truly" off.

I'm sure it's related to the "Ultra USB Power" port because:

• if the issue is happening (i.e. powered USB hub is connected to the "Ultra USB Power" port, PC is off, fans are spinning) and I then unplug the powered USB hub, the fans stop spinning. If a moment later I plug the powered USB hub in again to the "Ultra USB Power" port, the fans start to spin again (while the computer is off the whole time).
• turning the PSU off, and even unplugging the power cable, doesn't stop the fans from spinning if the powered USB hub is plugged in to the "Ultra USB Power" port

What is going on? Is there a setting I can turn on/off to disable this behaviour?
The powered USB hub seems to be a factor in this, because when connecting a hard drive directly, or my KVM switch, or other devices to the "Ultra USB Power" ports, everything is normal. The hub in question is Powered USB Hub Acasis 7 Ports 36W USB 3.0 Data Hub with Individual On/Off Switches 12V/2A if that matters
The case fans are all connected to the ARGB/PWM hub except for one that's connected directly to the motherboard.
I have tried updating and resetting the BIOS, didn't help.

 

[Misgar]

You might find this interesting:
https://forums.tomshardware.com/threads/usb-ports-on-motherboards.3716281/

I think you've already found a solution. Don't connect the powered hub to the Ultra USB Power ports.

You'd need a "diode OR" circuit to prevent +5V from the external hub's PSU feeding back into the PC via the Ultra USB ports. With diodes placed in strategic locations, the external hub's +5V supply would be blocked by a reverse biassed diode.

https://en.wikipedia.org/wiki/Diode-or_circuit

It's not the sort of modification which I'd recommend, even using MOSFETS or Schottky diodes with low forward drop voltages, but it's commonly used in electronics where you don't want this sort of power supply feedback.

I use several external harddrives that are connected to a powered USB hub

Are they small 2.5" portable hard disks, or larger 3.5" desktop hard disks. or perhaps they're SSDs? I find that a single 2.5" hard disk runs quite happily from a USB2 port with its built-in 500mA current limit. I run my 3.5" desktop hard disks off their own individual +12V supplies.

You should be able to run two 2.5" hard disks off a standard USB3 port with a 900mA current limit via a passive (unpowered) hub. If you have more than two 2.5" hard disks, you could try running them from a passive hub connected to an Ultra USB Power port. Disconnect the external PSU from the hub and see what happens.

 

[amerkiller]

You might find this interesting:
https://forums.tomshardware.com/threads/usb-ports-on-motherboards.3716281/

I think you've already found a solution. Don't connect the powered hub to the Ultra USB Power ports.

You'd need a "diode OR" circuit to prevent +5V from the external hub's PSU feeding back into the PC via the Ultra USB ports. With diodes placed in strategic locations, the external hub's +5V supply would be blocked by a reverse biassed diode.

https://en.wikipedia.org/wiki/Diode-or_circuit

It's not the sort of modification which I'd recommend, even using MOSFETS or Schottky diodes with low forward drop voltages, but it's commonly used in electronics where you don't want this sort of power supply feedback.


Are they small 2.5" portable hard disks, or larger 3.5" desktop hard disks. or perhaps they're SSDs? I find that a single 2.5" hard disk runs quite happily from a USB2 port with its built-in 500mA current limit. I run my 3.5" desktop hard disks off their own individual +12V supplies.

You should be able to run two 2.5" hard disks off a standard USB3 port with a 900mA current limit via a passive (unpowered) hub. If you have more than two 2.5" hard disks, you could try running them from a passive hub connected to an Ultra USB Power port. Disconnect the external PSU from the hub and see what happens.

Thanks for the reply!
Indeed, after posting this thread I discovered more of these threads so at least I'm glad I'm not alone with this issue.
That "diode OR" circuit thing is definitely overkill for my purpose.
As for not connecting the USB hub to the Ultra USB Power ports, the thing is that the Ultra USB Power ports provide better speeds compared to the other USB-A ports. I noticed this when doing my regular file transfers. You can see the speeds below:

I tried disconnecting the power supply from the powered USB hub, thinking that maybe one of these "Ultra USB Power" ports could power it but nope.
I read about data only USB cables but couldn't find any modern ones, only USB 2.0 ones.
In the end, I have ordered a USB-A (female) to USB-C (male) adapter (specifically Type C to USB Adapter USB-C 3.1 OTG A Female Data Connector Converter 10Gbps) I'll post back whether this solves the problem or not.