Here's the same track with the slightly lower sample rate of 176.4 (not 172 as I said in error above)
The CPU load is below 5%
 

I know your question is why the quantum leap in increasing CPU... but just logically speaking, at some point, your OS and your DAW will start FIGHTING for resources, which then adds overhead to the CPU to manage this war, which might be causing the QUANTUM leap.
 
I am using an APOLLO  (original old silver face) and can run in 192kz/24 bit, albeit I have to turn up the latency buffers on the Apollo/SPLAT to do this.  Which isn't an issue, since I can monitor the input tracks in real time and then it doesn't matter for mixing (except I notice a lag when I push the sliders and buttons).
 
I am totally guessing on what is causing the Quantum Leap.... 
 
 
PS - I also had a similar problem a few years ago, and using the same theory, fixed my DAW by turning down the number of threads that SPLAT would use (to be one less that my CPU had) so that the OS wasn't contending for CPU cycles but I think that the bakers have put in some fix for this since then.

Do you see the same difference inSonars CPU meters as you do in the Windows task manager?

Is the reading in the Task Manager the same for the whole song.

jimkleban
I know your question is why the quantum leap in increasing CPU... but just logically speaking, at some point, your OS and your DAW will start FIGHTING for resources, which then adds overhead to the CPU to manage this war, which might be causing the QUANTUM leap.
 
I am using an APOLLO  (original old silver face) and can run in 192kz/24 bit, albeit I have to turn up the latency buffers on the Apollo/SPLAT to do this.  Which isn't an issue, since I can monitor the input tracks in real time and then it doesn't matter for mixing (except I notice a lag when I push the sliders and buttons).
 
I am totally guessing on what is causing the Quantum Leap.... 
 
 
PS - I also had a similar problem a few years ago, and using the same theory, fixed my DAW by turning down the number of threads that SPLAT would use (to be one less that my CPU had) so that the OS wasn't contending for CPU cycles but I think that the bakers have put in some fix for this since then.

I apologize - what is SPLAT?

mudgel
Do you see the same difference inSonars CPU meters as you do in the Windows task manager?

Is the reading in the Task Manager the same for the whole song.

The Sonar CPU meters were the first clue - right after the audio engine crapped out. I turned on resource manager which confirmed the sonar executable was using up 4 cores at 40-50%.

I ran the same hi sample rate files through Ableton Live 9 and the results were
176.4  CPU @25%
192     CPU @52%
 

My question is purely academic. I have no intention of ever using 24/192 KHz for recording. It doesn't make sense.  There are plenty of summarized and detailed readings on that topic. http://productionadvice.co.uk/high-sample-rates-make-your-music-sound-worse/
 
There is also the risk of IM distortion introduced when down-sampling. See the SRC tests at http://src.infinitewave.ca/
where Sonar (since 8.5 onward) comes out looking pretty well top of the list for DAW's.
 

SPLAT is  "Sonar Platinum"