I was doing some test earlier and measuring the Task Manager CPU reading :
 
http://forum.cakewalk.com/Test-i7-2600K-vs-i7-6700K-HDD-none-Raid-vs-SSD-Raid-0-m3439971.aspx
 
However, in a few other tests that I've not posted the result yet, I was loading the 6700K CPU to over 50% (with 100 tracks running 2 Pro Channel per track). After this test, to my horror.. the CPU would just stay at 15% load without ever coming down to 0, even though with no other application running. I was thinking it may be a memory bug or something.. I rebooted the system, same result, CPU loading at 15% @ 3.xx Ghz. I run Sonar with no project loaded - same 15% load @ 3.xx Ghz - if i refer back to my test - the initial track run was registering only a few % CPU, with variable speed.
 
Now, it would just stay at 15% load. A few background services added to this load, with the "System and compressed memory" leading the way.
 
Searching on this issue "System and compressed memory" pops up a few topic regarding disabling "fast start" - a Windows 10 feature to save an image at shut down, so your next startup is faster. I tried all sort of setting following this path with no help - CPU load still at 15%.
 
I re-installed Windows 10 - same result.
 
I'm wondering if it's my SSD being overworked - as the Task Manager also shows 100% 'active' on the boot disk from time to time. I'm letting the system shut off till tomorrow and see.. 
 
Meanwhile, I would appreciate if you can check your Task Manager CPU load with no apps running - especially if you're using SSD too.
 
Note : My other 2600K system's CPU load is still at a nice 0% (occasionally going 1%) when no other apps running - and I've not (don't dare to) run the 100 Tracks with 2 PC per track test on this system!!
 
Thanks!

So.. after about an hour rest the 6700K CPU % usage is now at a nice 0% as usual.. I wonder why it behaves so. And the "system and compressed memory" no longer tops the CPU on idle usage.

It is normal for certain processes to run and use CPU, etc. when you are doing nothing.  "System and compressed memory" is one of these processes.  Windows 10 has a performance enhancement that uses idle CPU cycles to compress data in RAM so that more data can be stored using less memory.  Without getting too much into the technical details, this helps the operating system avoid having to write and read data to a hard drive which is typically much slower than accessing RAM even with the need to use CPU to decompress.  This is true even with SSDs.  As far as I know, it has nothing to do with fast start and you do not want to disable it or your system will overall run slower.  

Thanks Dave76. What I've noticed is that immediately after a few reboots / short shut down, the results are the same, but after an hour shut down it's back to low 0 or 1% usage. It should be ok in normal usage, just that the extra 15% bumps up the test results.
 
On the plus side (since I reinstalled Windows 10) - I got to test Windows re-activation without entering my Windows 8 code does work without issue.

Hmm, interesting, but thanks.

Recently a CompactOS option was added and the task runs for a long time compressing OS modules.
 
You can see this by typing this in an administrative command prompt:
 
>compact /CompactOS:query
The system is not in the Compact state. It will remain in this state unless an
administrator changes it.
 
That is my results because I disabled the compaction via one of the other compact options.