Question adding low frequency ram stick with high frequency ram stick

Apr 20, 2020
I switched my hyperx RAM stick 8gb-2133Mhz to 2 hyperx RAM sticks 8gb-2666Mhz. After many attempts of trying to switch on BIOS my ram frequency to 2666 from 2133,I found out that my motherboard doesn't allow to my CPU go over 2133Mhz of RAM frequency.My question is, can I add the 2133Mhz RAM stick so I will have 24gb of RAM, without any affect on the computer? I read that I shouldn't add a high frequency RAM stick with low frequency or it would affect the performance of my computer.
thank you!

CPU: Intel i7-6700 3.4Ghz
Go ahead and try it; no harm can come.
The ram will all run at the capability of the lowest performing ram, namely 2133.
That really is not a bad thing since the intel ram controller is very good at prefetching what it needs.
Real app performance of apps or fps is not much impacted by speed.
If the extra stick works, two of the 8gb sticks will work in dual channel mode and the odd stick will be in single channel mode.
This is called flex mode.

Memtest86 is the gold standard for testing ram.
It boots from a usb stick and does not use windows.

If you can run a full pass with NO errors, you should be ok.


Sep 26, 2019
Yes you can add slower RAM with the faster RAM and it will automaticly slow the faster RAM down to to speed of the slower RAM. In this particular case it won't change anything cause the motherboard is already slowing everything down to 2133 to start with.

In a normal scenario where the motherboard isn't limiting the RAM speed to start with, adding slow RAM to fast RAM would slow down your computer cause it would slow down all the other RAM sticks to it's own speed. It would work and you would have more total RAM capacity, it just wouldn't be optimum. But in this case it doesn't hurt anything and will give you more RAM.