MP 1,1-5,1 USB struggles (Mojave)

[Cave Man]

My Mac Pro 5,1 (12-core, 128 GB RAM, RX 580 with latest firmware, 4 TB SSD) is working pretty well, except for a recurrent issue with USB. It seems that after the computer has been on for 24-48 hours, USB responsiveness declines (e.g., mounting an external SSD or flash drive slows to a crawl). This leads to need for a reboot. However, sometimes when I reboot, all the USB ports are nonfunctional. Then I reboot again and they work just fine. So, I'm struggling to determine what might be the cause of this.

I have no other PCI cards installed. Other than the RX 580, the 4 TB SSD and an internal 3 TB SATA HD, everything is OEM. Both the USB flash drive and the external SSD are USB3.

 

[tsialex]

Did you verified the RTC battery voltage?

When the BR2032 voltage is too low and the RTC counters becomes stuck, one of the things that behave crazily is USB.

 

[Cave Man]

OK, thanks much. I just replaced the battery and the USB ports seem to be working. I'll keep checking once a day to see if it's resolved. Appreciate the tip!

 

[Cave Man]

Well, the computer has been on for almost a week and all is stable. Thanks again for the battery tip. I would have never figured that one out.

Next, 802.11AC wifi update, probably via a PCI card just to keep it simple.