That's the way RAM speed is measured in dual channel mode: 2x800MHz=1600MHz.

THIS IS WHAT I FOUND SO FAR FOR AN EXPLANATION
1) You set the timings in the BIOS, so no matter what a Windows program reads it, it is running at the BIOS speed.
2) In CPU-Z, you have to times...

I am having the same isssue my 1600mhz ram is capped at 800mhz Bios shows it set to 1600mhz . 16gb of ram installed only using 2.1 gb of the 16gb . No idea whats going on . All drivers cpu/gpu are...