Intel S975XBX2 Product Specification - Page 28

Intel Workstation Board S975XBX2 Technical Product Specification 1.7 PCI Express Connectors The board provides the following PCI Express connectors: • One Primary PCI Express x16 (electrical x16 or x8) bus add-in card connector. The x16 interface supports simultaneous (full duplex) transfers up to 8 GBytes/sec. Single-ended (half duplex) transfers are supported at up to 4 GBytes/sec. • One Secondary PCI Express x16 (electrical x8) bus add-in card connector: The board provides a PCI Express add-in card connector in the form of a physical x16 connector with electrical routing of x8. This connector is an electrical equivalent of a PCI Express x8 bus add-in card connector. This connector also supports x4 and x1 PCI Express add-in cards. • One PCI Express x16 (electrical x4) bus add-in card connector: The board provides a PCI Express add-in card connector in the form of a physical x16 connector with electrical routing of x4. This connector is an electrical equivalent of a PCI Express x4 bus add-in card connector. This connector supports x4 and x1 PCI Express add-in cards. For optimum performance, observe the following recommendations for the PCI Express add-in card connectors: • If you are installing a single PCI Express Graphics card, install it in the Primary PCI Express x16 (electrical x16 or x8) bus add-in card connector. • If you are installing two PCI Express Graphics cards, install them in the Primary PCI Express x16 (electrical x16 or x8) bus add-in card connector and the Secondary PCI Express x16 (electrical x8) bus add-in card connector. The PCI Express interfaces for the Primary and Secondary PCI Express x16 connectors are routed through the MCH. The PCI Express interface for the PCI Express x16 (electrical x4) connector is routed through the ICH7-R/ICH7-DH. Therefore, the Primary and Secondary PCI Express x16 connectors provide higher performance than the PCI Express x16 (electrical x4) bus add-in card connector. For information about The locations of the specific PCI Express x16 add-in card connectors Refer to Figure 1, page 14 # INTEGRATOR'S NOTE Although the PCI Express specification allows x16 cards to auto-negotiate down from x16 to x4 and x1 and may function properly, such configurations have not been validated on this board. Please consult your add-in card vendor prior to attempting to use a PCI Express x16 add-in card in this connector. The PCI Express interface supports the PCI Conventional bus configuration mechanism so that the underlying PCI Express architecture is compatible with PCI Conventional compliant operating systems. Additional features of the PCI Express interface includes the following: • Support for the PCI Express enhanced configuration mechanism • Automatic discovery, link training, and initialization • Support for Active State Power Management (ASPM) 28