User Guide

Hardware Functional Overview
4-12 FIC MD02 Service Manual
incorporates the functionality of two 82C59 interrupt controllers. The two interrupt
controllers are cascaded so that 14 external and two internal interrupts are possible. In
addition, the ICH4 supports a serial interrupt scheme.
All of the registers in these modules can be read and restored. This is required to save and
restore system state after power has been removed and restored to the platform.
Advanced Programmable Interrupt Controller (APIC)
In addition to the standard ISA compatible Programmable Interrupt Controller (PIC)
described in the previous section, the ICH4 incorporates the Advanced Programmable
Interrupt Controller
Universal Serial Bus (USB) Controller
The ICH4 contains an Enhanced Host Controller Interface (EHCI) compliant host ontroller
that supports USB high-speed signaling. High-speed USB 2.0 allows data transfers up to
480 Mb/s which is 40 times faster than full-speed USB. The ICH4 also contains three
Universal Host Controller Interface (UHCI) controllers that support USB full-speed and low-
speed signaling.
The ICH4 supports 6 USB 2.0 ports. All six ports are high-speed, full-speed, and low-
speed capable. ICH4’s port-routing logic determines whether a USB port is controlled by
one of the UHCI controllers or by the EHCI controller. See Section 5.16, “USB UHCI
Controllers (D29:F0, F1 and F2) and Section 5.17, “USB EHCI Controller (D29:F7) for
details.
LAN Controller
The ICH4’s integrated LAN Controller includes a 32-bit PCI controller that provides
enhanced scatter-gather bus mastering capabilities and enables the LAN Controller to
perform high speed data transfers over the PCI bus. Its bus master capabilities enable the
component to process high-level commands and perform multiple operations; this lowers
processor utilization by off-loading communication tasks from the processor. Two large
transmit and receive FIFOs of 3 kB each help prevent data underruns and overruns while
waiting for bus accesses. This enables the integrated LAN Controller to transmit data with
minimum interframe spacing (IFS).
The LAN Controller can operate in either full duplex or half duplex mode. In full duplex
mode the LAN Controller adheres with the IEEE 802.3x Flow Control specification. Half
duplex performance is enhanced by a proprietary collision reduction mechanism. See
Section 5.2, “LAN Controller (B1:D8:F0)” on page 5-78 for details.
RTC
The ICH4 contains a Motorola* MC146818A-compatible real-time clock with 256 bytes of
battery-backed RAM. The real-time clock performs two key functions: keeping track of the
time of day and storing system data, even when the system is powered down. The RTC
operates on a 32.768 KHz crystal and a separate 3-V lithium battery that provides up to
seven years of protection.
The RTC also supports two lockable memory ranges. By setting bits in the configuration
space, two 8-byte ranges can be locked to read and write accesses. This prevents
unauthorized reading of passwords or other system security information.
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