Overview of PCI Express (PCIe) Operation
007-5832-002 63
Overview of PCI Express (PCIe) Operation
This section provides a brief overview of the PCI Express (PCIe) technology 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
specific PCI Express board options available with the SGI UV 2000.
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 6-1)
• Potential sustained throughput of x16 PCI Express is approximately four times that of the
fastest PCI-X throughputs
Figure 6-1 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 - also called “by 1”.
PCI 2.0 32-bit
PCI Express x1
CI Express x16