PCI Express is the third generation of multi-purpose I/O interface that can
be used across the computing industry, from mobile through high-end servers and
communication equipment. Cabled PCI Express targets a large number of
applications such as removable media drives (e.g., CD/DVD), memory modules, I/O
ports (e.g., USB, IEEE-1394), and audio jacks, conventional PCI Express add-in cards
(with or without Hot-Plug support) and/or ExpressModules, Location of the graphic subsystem (i.e., controller and memory) external
to the main systems unit.

PCI Express is the third generation of multi-purpose I/O interface that can
be used across the computing industry, from mobile through high-end servers and
communication equipment. The broad usage and versatility of this technology
allows for system extensions to external input/output Subsystems that meet the
needs for specific target applications and/or environments.

Cabled PCI Express targets a large number of applications, including but not
limited to:

  • Split-systems, or disaggregate PCs, with a desktop “console” that contains
    removable media drives (e.g., CD/DVD), memory modules, I/O ports (e.g., USB,
    IEEE-1394), and audio jacks
  • I/O expansion to extend the I/O card capabilities of the main system for
    support of different form factors, including legacy, test and measurement, and
    instrumentation equipment
  • Server expansion I/O to support conventional PCI Express add-in cards
    (with or without Hot-Plug support) and/or ExpressModules
  • Location of the graphic subsystem (i.e., controller and memory) external
    to the main systems unit

System-level support for cabled PCI Express is possible through
implementation on expansion cards; e.g., PCI Express CEM, ExpressModules, PXI
Express, ExpressCard, or direct from a system board. This specification defines
connectors for supporting a x1, x4, x8, and x16 cabled copper PCI Express Links.
Other Link widths, such as x2, might be added in subsequent revisions of this
specification.