I am seeing around 50% CPU load when Raytraced is running here too.
V7 on a dual 6 core Xeon (=total of 12 cores and 24 threads)
Intel denoiser turned on in render settings.
When in Rendered mode and Rhino idle in the background the CPU load is 6%.
When I turn off Rhino it drops to 2%.
That is with the intel denoiser turned off.
File saved and reopened and idle CPU load is 2%.
When Raytraced view is activated it is now around 50% CPU load again (intel denoiser still off)
When Raytraced is competed (100 of 100 cycles) the cpu idles at 6% again.
And NOW when switched to Rendered it drops down to 2% again.
So cycles seems to hog some cpu usage even when idle, and if the intel denoiser was used it continues to hog those resorses even after raytraced is turned off.
Edit: I restart Rhino after each change to make sure nothing is left unchanged.
Tried with the nvidia denoiser now and then the cpu is used 50% when rendering and idles at 11% when completed. And goes down to 6% when switched to rendered mode. So still hogging resources.
On restart with no denoiser I see the same again, when Raytraced it uses 50% cpu load and drops to 6% cpu when completed, and again drops to 2% when switched to Rendered.