HP XA The PIIX4, PCI/ISA Bridge Chip (82371AB)

2 System Board

Chip-Set

The PIIX4, PCI/ISA Bridge Chip (82371AB)

The universal host controller interface (UHCI) chip, known as PIIX4, is encapsulated in a Ball Grid Array (BGA) package.

The PIIX4 chip is a multi-function PCI device implementing a PCI-to-ISA bridge function, a PCI IDE function, a Universal Bus host/hub function, and an Enhanced Power Management function.

The following figure shows an example of the system block diagram using the PIIX4 chip.

Second Level	Processor
Cache

Host Bus

	AGP Bus	Host-to-PCI	Memory Bus	Main Memory
Cirrus AGP
		Bridge		DRAM
CL5465

PCI Bus (3.3V or 5V, 30/33 MHz)

Hard Disk	Hard Disk
				USB 1	PCI Slots
		BMI IDE	PCI/ISA Bridge (PIIX4)	USB2
		Ultra DMA/33	82371AB	GP[I,O] (30+)
				SM Bus

CD-ROM

Audio	KBD	SP, PP,	BIOS
		FDC, IR

ISA/EIO Bus (3.3V; 5V Tolerant)

32