CPU: i5 2500k @4,2 Ghz
GPU: Sapphire R9 390X 8 Gb - newest Crimson Driver RAM:
16 GB DDR3
OS: Windows 10 x64
Display: LG 29 UM 68-p 21:9 Display (2560x1080). Freesync enabled, previously tuned Freesync but now removed the tuning with CRU. All display drivers freshly new installed.
Memory clock alternates between 150 and 1500 Mhz in windows. Only when moving the mouse/surfing on the web. When idling memory clock is at 150 Mhz, but standard websurfing (no complex HTML5 sites, just a bit wikipedia/reddit) with Chrome (GPU acceleration disabled) or Microsoft Word usage lets the memory clock alternating.
Here is a graph (orange line!)
I'm having this problem too, and I think its making youtube and general browing way more laggy, only noticed it during a recentish driver upgrade. My specs are pretty similar, still a problem in latest driver using MSI R9 390x