Trying to diagnose why Sonar shows 90+% CPU load and Windows 10 Task Monitor reads only 25%.
My theory is an old BIOS.  From 2011!  There have been no updates!
 
What else could it be?

Sonar looking at one core and Task Manager shows overall CPU use?
 

Sonar displaying one huge core and seven little cores...hmmm.
Task Monitor showing 8 cores, all equal.

Not sure how to get Sonar to use more than one core, which it looks like its doing.  Maybe Jim Roseberry can answer this.
 

Depends on numerous factors.
Is the Use Multiprocessing Engine option enabled?
Is the Plugin Load Balancing option enabled?
 
Another thing to try:
Uncheck the Plugin Load Balancing option
Go to the Configuration File; set Enable Set Thread Ideal Processor to "False" and set Mix Thread Count to one less than the total number of processing threads for your CPU.
ie:  If you're running a 8700k (six cores, 12 processing threads), you'd set this to 11.
 
Some plugins like UVI Falcon can't use multiple CPU cores.
Not all processes in a DAW can be multi-threaded.
This is why high clock-speed is important.

Plugin Load Balancing was unchecked.  Ugh.

The CPU module can be set to show three different displays Thedoccal

1. Audio Performance
2. System Performance
3. Overall App Performance

Right click on the CPU Module and select from the CPU Meter Options.