Ok y'all just upgraded my mobo and had to get new ram because my old ram wouldn't...

[Charles Colvin]

Ok y'all just upgraded my mobo and had to get new ram because my old ram wouldn't work. It was the correct speed and everything. Now I have 8gbs installed and the bios recognized that it is all there but says only 4 of it is usable. Plus it is lowering my speed from 2133 to 1600. I know a bit outdated but it is a few years old. I had already tried switching them and different slots. All of the slots work.
EDIT: I have tried to manual up the ram speed in bios ,but after it resets, it no longer detects the ram until I reset the computer again and it slows it down.
Specs:
Mobo:970 pro gaming/aura
Cpu:AMD-8350 4.0GHz.
Ram(currently installed) EVGA 4gbx2 DDR3-2133
(Ram that wouldn't work) G.skill ripjaws X 8gbx2 DDR3-1866
Video Card:Saphire Radeon R9 280

 

[Andrew Cobb]

1600 is stock, tell your motherboard to clock the ram to 2133mhz

 

[Robert Mendola]

Some windows versions limit maximum ram, which one are you running