HP Compaq dc7800 MT, Technical Reference Manual

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Technical Reference Guide www.hp.com 4-1
4
System Support
4.1 Introduction
This chapter covers subjects dealing with basic system architecture and covers the following
topics:
■
PCI bus overview (4.2)
■
System resources (4.3)
■
Real-time clock and configuration memory (4.4)
■
System management (4.5)
■
Register map and miscellaneous functions (4.6)
This chapter covers functions provided by off-the-shelf chipsets and therefore describes only
basic aspects of these functions as well as information unique to the systems covered in this
guide. For detailed information on specific components, refer to the applicable manufacturer's
documentation.
4.2 PCI Bus Overview
✎
This section describes the PCI bus in general and highlights bus implementation for systems
covered in this guide. For detailed information regarding PCI bus operation, refer to the
appropriate PCI specification or the PCI web site: www.pcisig.com.
These systems implement the following types of PCI buses:
■
PCI 2.3 - Legacy parallel interface operating at 33-MHz
■
PCI Express - High-performance interface capable of using multiple TX/RX high-speed
lanes of serial data streams
4.2.1 PCI 2.3 Bus Operation
The PCI 2.3 bus consists of a 32-bit path (AD31-00 lines) that uses a multiplexed scheme for
handling both address and data transfers. A bus transaction consists of an address cycle and one
or more data cycles, with each cycle requiring a clock (PCICLK) cycle. High performance is
achieved during burst modes in which a transaction with contiguous memory locations requires
that only one address cycle be conducted and subsequent data cycles are completed using
auto-incremented addressing.
Devices on the PCI bus must comply with PCI protocol that allows configuration of that device
by software. In this system, configuration mechanism #1 (as described in the PCI Local Bus
specification Rev. 2.3) is employed.