Issues with bottom RAM-slot MBP 2012 - MacBook Pro 13

how do i test for a bad memory slot ? ram slot 3 and 4 not working Try to fill 4 memory slot and check if display is coming or not Also refer TPS of this mbd , page 18 , ur ram is 1Gbx64 , but for 8GB they ramses legacy slot I bought four 8GB RAM sticks for the four slots on the motherboard I can only get the BIOS to see two of the four at a time… If I take a

ramesses book slot demo B550M DS3H ; 1 Solid Pin Power Connector ; 2 DVI ; 3 DisplayPort + HDMI ; 4 Realtek GbE LAN ; 5 Ultra Durable PCIe Slot · PCIe® Slot · Running 1*