Wrong RAM speed for my motherboard

Primegaming10

Reputable
Feb 15, 2015
27
0
4,540
So i just built a new computer for my Dad and i used the most cheapest parts i could and i ended up taking ram from my old computer that had a intel core i5 750 and other cheap stuff, and i put the ram into the computer and the computer is a bit slow it is running a Pentium g3258 anniversary and i am pretty sure that the computer should be able to run windows rile opener thing and it even lags when i open the internet and ends up say NOT RESPONDING a lot i cant tell what the RAMs mhz are at tho so could someone pls help