Hi Allan
Initially I used the desktop CPU/Memory gadget and Task manager to monitor the CPU load, I then used a program called Process Explorer to track down the individual process. After noting the process was the USB 3 driver, I then measured the system with and without the driver installed several times. In every case the CPU started to idle at 27%-30% when all USB connections were removed or powered down with the USB 3.0 eXtensible Host Controller driver 2.5.3.34 installed. As soon as I inserted a thumb drive or powered up the DAC the CPU idle dropped to ~1%
My test configuration is simply a high end audio DAC with a 2.0 USB interface that is powered down when not in use. The NUC is powered 24 x 7
The idle issue can actually happen in less than 2 hours and does not appear to be temperature related in any way. A re-boot will always fix the issue until a USB 3 port is used again. The issue is indifferent to which of the front or back USB ports are used.
I initially found the issue running BIOS Ver.26 . After updating with Ver.27 I confirmed the issue was still present.
My installation is headless and controlled using Event Ghost running TCP commands. The ONLY connections to the NUC are one USB and the Ethernet connection. All measurements were made utilising Microsoft Remote Desktop. In respect to software applications and drivers installed, the NUC has a DAC driver and an Audio player called J River Media Centre. Aside from the Process Explorer diagnostic software all other drivers are those recommended and supplied by Intel.
I only have access to one NUC system that supports USB 3.0. The system I have has been running flawlessly for the last three days with the USB 3.0 eXtensible Host Controller driver removed.
Fortunately my application does not need USB 3 speeds, nevertheless it would be in everyone’s interest to resolve the anomaly.
Regards
Chris