Pci Bus Overview - HP Deskpro EX Technical Reference Manual

Chapter 4 System Support
4.2

PCI BUS OVERVIEW

NOTE: This section describes the PCI bus in general and highlights bus implementation
in this particular system. For detailed information regarding PCI bus operation, refer to
the PCI Local Bus Specification Revision 2.2.
This system implements a 32-bit Peripheral Component Interconnect (PCI) bus (spec. 2.2)
operating at 33 MHz. The PCI bus handles address/data transfers through the identification of
devices and functions on the bus. A device is typically defined as a component or slot that resides
on the PCI bus (although some components such as the GMCH and ICH are organized as multiple
devices). A function is defined as the end source or target of the bus transaction. A device may
contain one or more functions.
In the standard configuration these systems use a hierarchy of three PCI buses (Figure 4-1). The
PCI bus #0 is internal to the 815 chipset components and is not physically accessible. The AGP
bus that services the AGP slot (or resident AGP controller on the EN SFF) is designated as PCI
bus #1. All PCI slots reside on PCI bus #2.
Mem. Cntlr.
Function
Hub Link I/F
Hub Link I/F
PCI Bridge
Function
Figure 4-1. PCI Bus Devices and Functions
4-2 Compaq Deskpro EX Series of Personal Computers
82815 GMCH Component
PCI
AGP
Bus #0
Bridge
Function
Hub Link Bus
EIDE
Controller
Function
PCI
Bus #2
PCI Connector 1
PCI Connector 2
PCI Connector 3
First Edition - August 2000
PCI Bus #1
(AGP Bus)
AGP Connector
82801AA ICH Component
PCI Bus #0
USB SMBus
I/F Controller
Function Function
LPC AC97
Bridge Audio
Function Function