Intel SGI Altix 450 manual Overview of PCI Express Operation

Overview of PCI Express Operation

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

PCI 2.0 32-bit

PCI Express x1

PCI Express x16

Figure 6-14Comparison 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

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