How come when I install three double-sided memory modules in the 5011H Superserver, it only recognize the first two memory modules? If I put one in slot three by itself, it only recognizes half the size. Do I have a bad memory slot?
No, your Superserver doesn't have a bad memory slot. The 5011H uses the Intel 815 chipset motherboard P3TSSR, which only supports up to 4 banks of memory. Since this board has 3 memory sockets, if you use double-sided memory modules then you can only use the first two sockets. (2 sided x 2 modules = 4 banks). If you use single-sided memory then you can use all three memory sockets.