Ram not at full speed?

Groundphoenix

Commendable
Jan 8, 2017
12
0
1,510
So I have the Asus ROG Strix Z270E Gaming Motherboard that supports up to 3866 MHz, I bought the G.Skill TridentZ Series 3733 MHz as the 3866 was sold out...after installing the OS, I restarted my PC and looked at the bios, and it says the RAM is running at 2133 MHz, is it running at that speed because of my CPU or can I do something...
 

Groundphoenix

Commendable
Jan 8, 2017
12
0
1,510
If anyone is able to respond...i wanna get the new TridentZ RGB series DDR4 Ram, I currently have 2 of the TridentZ Series DDR4 3733MHz, but I can't seem to find that speed in the RGB series...would I be able to pair them if I purchase a higher or lower speed..like the 3866 or the 3600???