50
2 System Board
The Input/Output Controller Hub (82801AA)
ICH Architecture
The ICH interface architecture ensures that the I/O subsystems, both PCI
and the integrated input/output features (for example: IDE, AC’97 and USB)
receive the adequate bandwidths.
To achieve this, by placing the I/O bridge directly on the ICH interface, and
no longer on the PCI bus, the ICH architecture ensures that both the
input/output functions integrated into the ICH and the PCI peripherals
obtain the bandwidth necessary for peak performance.
ICH PCI Bus Interface
The ICH PCI provides the interface to a PCI bus interface operating at
33 MHz. This interface implementation is compliant with PCI Rev 2.2
Specification, supporting up to six external PCI masters in addition to the
ICH requests and AC’97 controller. The PCI bus can reach a data transfer
rate of 133 MBytes/sec. The maximum PCI burst transfer can be between
256 bytes and 4 KB. It also supports advanced snooping for PCI master
bursting, and provides a pre-fetch mechanism dedicated for IDE read.
Refer to
page 68
for a description of the devices on the ICH.
SMBus Controller
The System Management (SM) bus is a two-wire serial bus. It runs at a
maximum of 100 kHz. The SMBus Host interface allows the processor to
communicate with SMBus slaves. The bus connects to sensor devices that
monitor some of the hardware functions of the system board, both during
system boot and run-time.
Refer to
page 55
for a description of the devices on the SMBus, or to
page 58
for information on the MaxiLife ASIC.
Low Pin Count Interface
The ICH implements the LPC interface 1.0 specification.
Enhanced USB Controller
The USB (Universal Serial Bus) controller provides enhanced support for
the Universal Host Controller Interface (UHCI). This includes support that
allows legacy software to use a USB-based keyboard and mouse. The USB
supports two stacked connectors on the rear panel. These ports are built
into the ICH, as standard USB ports.
The ICH is USB revision 1.1 compliant.
USB works only if the USB interface has been enabled within the HP
Setup
program. Currently, only the Microsoft Windows 95 and Windows 98
operating systems provide support for the USB.
