You with have 8/10 pins on the top/back of each unit. There should be a diagram on how to make them master + Slave as they both won't work until they are on different settings! It's a little black piece of plastic with a metal connector inside. They slide over 2 of the 8/10 pins to tell the motherboard what's going on... They both have to be different. Just look at the sticker on the unit its-self..