Instruction Manual

Figure 5. PCI RS/6000 Entry Server Logical Block Diagram
2.1.1 The PCI Bus Architecture
The Peripheral Component Interconnect (PCI) is a specification standard for
computer bus implementation developed by the PCI Special Interest Group
(PCI-SIG), led by a group of companies including Compaq, Digital, IBM, Intel and
NCR. There are now over 300 companies in the PCI-SIG supporting the
architecture and currently producing PCI products.
The goal was to provide a common system-board bus that could be used in
personal computers, from laptops to servers. It was envisioned as a local system
board bus that would serve as a common design point, supporting different system
processors as the various processors evolved over time. This is much like
operating systems which have defined Application Binary Interfaces (ABIs) so that
applications need not change with each generation of the operating system. The
PCI Local Bus would serve as a common hardware interface that would not change
with different versions of microprocessors.
The group defined PCI to support the high-performance basic system I/O devices,
such as the graphics adapter, hardfile controller and/or LAN adapter. In the original
definition, these would be mounted on the planar and would communicate through
the PCI bus. Current I/O buses (ISA, EISA and Micro Channel) would be used to
attach pluggable features to configure the system for the desired use. The first
release of PCI Specification was made available in June of 1992.
The PCI Special Interest Group (SIG) soon realized that the PCI bus needed the
capabilty to support connectors. For example, display controller evolution doesn't
necessarily match planar development; so providing for an upgrade of the display
controller became a requirement. The next release of the PCI Specification
12 Introduction to PCI-Based RS/6000 Servers