I've had a problem for a while that I've only now had the time to look into.

My WHS has an Athlon X2 64 5000+ CPU.   Quite often one of the cores in the CPU will just start working overtime and max its performance.  The other core stays at normal usage. 

Nothing shows in the processes list that stands out as using any of the CPU, and memory usage is pretty standard too.  When this happens my RDP access to the server slows to a crawl, responsiveness of applications on the server slows (eg browsing windows explorer).  The WHS console is not running when this happens.  

The only computers connected to the WHS are a Mac mini running OSX, also running Plex that accesses some shared video folders on the WHS.  When this happens the access to the folder shares slows and any videos that are playing time out and stop playing.  I then can't start them again until such time as the CPU comes back to normal, usually 5-10 minutes later.

There are no other applications running in the taskbar or the background.  I suspect it has to do with folder duplication, as I can hear some disk access while it's happening. I have about 80GB free of a 4.5TB server storage pool.

I've installed the AMD processor drivers but this made no difference, all Windows updates are applied, and all other drivers are up to date.   

There's no real regularity to the timing of this, just seems to do it whenever it's most inconvenient :)

Anyone out there have any ideas what might be causing this?  Or how I can investigate the processes further - beyond the standard Task Manager list that doesn't seem to be giving any clues away?  

Here's a screenshot: