What form factor/size is your 9020? What do you have in it for RAM?  Brand and model numbers are helpful. [IMAGE]  
i have dell optiplex 9020 with i7-4790 and i installed 4 slots of ram but in the system it only uses 2 slots of ram. so how do i enable full slots ? 
i have dell optiplex 9020 and i want to enable 4 ram slots ?