Power Mac G5 Black screen

Hey, I bought an old power Mac G5 2.3 DP pci-x but it did not have ram or a gpu, I’ve just received the gpu but I’m not getting a sound or a video output in fact, my monitor does not even react when I power the Mac on. It’s a Radeon ATI 9600 AGP. My only guess is that I need ram to get a video signal for some reason. But I’m still worried because after looking at the gpu and the a lot on the motherboard it seems like I’m missing something.