Computer Busses

5

Motherboard Design

5.1 Introduction

This chapter analyses a Pentium-based motherboard. An example board is the Intel 430HX motherboard which supports most Pentium processors and has the following component parts:

• PCIset components – 82438 System Controller (TXC) and 82371SB PCI ISA Xcelerator (PIIX3).

• 82091AA (AIP) for serial and parallel ports, and floppy disk controller.

• DRAM main memory.

• L2 cache SRAM.

• Universal serial bus (USB).

• Interface slots (typically 4 PCI and 3 ISA).

• 1 Mbit flash RAM.

Figure 5.1 illustrates the main connections of the PCIset (which are the TXC and PIIX3 devices). The TCX allows for a host-to-PCI bridge, whereas the PIIX3 device supports:

Figure 5.1 PCIset system architecture

• PCI-to-ISA bridge.

• Fast IDE.

• APIC ...