PCI Express System Architecture

Predecessor Buses Compared

In an effort to compare and contrast features of predecessor buses, the next section of this chapter describes some of the key features of IO bus architectures defined by the PCI Special Interest Group (PCISIG). These buses, shown in Table 1-1 on page 12, include the PCI 33 MHz bus, PCI- 66 MHz bus, PCI-X 66 MHz/133 MHz buses, PCI-X 266/533 MHz buses and finally PCI Express.

Table 1-1. Bus Specifications and Release Dates

Bus Type	Specification Release	Date of Release
PCI 33 MHz	2.0	1993
PCI 66 MHz	2.1	1995
PCI-X 66 MHz and 133 MHz	1.0	1999
PCI-X 266 MHz and 533 MHz	2.0	Q1, 2002
PCI Express	1.0	Q2, 2002

Author's Disclaimer

In comparing these buses, it is not the authors' intention to suggest that any one bus is better than any other ...