Question low gpu and cpu usage low temp

[3NERGY]

what ram speeds ( ddr3 ) can i use on my i7 3770
i have low gpu and cpu usage and old dell optilex 7010 mobo
my gpu is gtx 1070fe
temps are good
so i think fault is mobo or ram so 2 questions

1) what mhz ram can i use on my cpu right now

2)what mhz ram can i use on my cpu if i had different mobo

 

[3NERGY]

i7 3770 official site says 1333/1600mhz but i saw some people having 2400mhz ram on i7 3700