CPU Type: Six/Four-Core ready AMD Opteron 4100 Series South Bridge: AMD SP5100 Number of DDR3 Slots: 4 x 240pin Maximum Memory Supported: 64GB ECC Supported: Yes Registered: Yes PCI Express x8: 1 x PCI-E 2.0 x8 in x16 1 x PCI-E 2.0 x8 PCI Express x4: 1 x PCI-E 2.0 x4 in x8