Random core frequency drop, FX8350

Hi guys, well I'm running my FX-8350 @4.7ghz stable and I have had a very odd issue occur. It has happened only twice but basically 3-6 cores will drop in frequency from 4.7ghz ro 1.4ghz or so. I'm using HWinfo64, and Coretemp to determine core usage and freq.

The drop seems to be random, for instance I just left my computer idle for about 15minutes, came back, was about to check my email but instead took a quick look at HWinfo 64 (Which I almost always keep running so I have an idea of where my temps and general usage stands). I noticed this time that 6 cores were at 1.4ghz and the other 2 wre still at 4.7ghz. There was no drop in Vcore, no drop in temps, no very noticeable difference in performance and also once I rebooted my pc all cores were back up to 4.7ghz. Is this a software issue or is my mobo scaling them down when idle to save power? I guess it isn't a big deal because it isn't affecting performance at all because I can just restart it also has only happened twice in 3 days. Any insight would be appreciated! Thanks!

My specs:

ASRock 990fx Professional Fatal1ty 12+2 power phase
FX8350@4.7ghz w/Noctua NH-C14
2x4GB Patriot Viper 3 1866mhz
2xGigabyte 7850 2GB DDR5
OCZ Vertex 4 128ssd for boot
XFX 750w Pro Core Edition 80plus Bronze