EPS12V - 24 pin main connector, 8 pin secondary connector, optional 4 pin tertiary connector (Xeon and Opteron) defined in SSI specification
ATX12V - 20 pin main connector, 4 pin secondary connector, 8 pin tertiary connector (Pentium 4 and mid/late Athlon XP & Athlon 64)
ATX12V 2.0 - 24 pin main connector, 4 pin secondary connector (Pentium 4, Core 2 Duo, and Athlon 64 with PCI Express)