Intel SGI Altix 450 - Manual (Page 149)

Overview of PCI Express Operation
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Overview of PCI Express Operation
This section provides a brief overview of the new PCI Express (PCIe) technology that will be
available as an option with your system. PCI Express has both compatibility and differences with
older PCI/PCI-X technology. Check with your SGI sales or service representative for more detail
on PCI Express options available with the SGI Altix 450.
PCI Express is compatible with PCI/PCI-X in the following ways:
• Compatible software layers
• Compatible device driver models
• Same basic board form factors
• PCIe controlled devices appear the same as PCI/PCI-X devices to most software
PCI Express technology is different from PCI/PCI-X in the following ways:
• PCI Express uses a point-to-point serial interface vs. a shared parallel bus interface used in
older PCI/PCI-X technology
• PCIe hardware connectors are not compatible with PCI/PCI-X (see Figure 6-14)
• Potential sustained throughput of x16 PCI Express is approximately four times that of the
fastest PCI-X throughputs
Figure 6-14 Comparison of PCI/PCI-X Connector with PCI Express Connectors
PCI Express technology uses two pairs of wires for each transmit and receive connection (4 wires
total). These four wires are generally referred to as a lane or x1 connection. This is also called “by
PCI 2.0 32-bit
PCI Express x1
PCI Express x16