Overview
The Intel® 450NX PCIset provides an integrated Host-to-PCI bridge and memory controller optimized for multiprocessor systems and standard high-volume (SHV) servers based on the Pentium® II Xeon™ processor variant of the P6 family. The Intel 450NX PCIset consists of four components: 82454NX PCI Expander Bridge (PXB), 82451NX Memory and I/O Bridge Controller (MIOC), 82452NX RAS/CAS Generator (RCG), and 82453NX Data Path Multiplexor (MUX). Figure 1-1 illustrates a typical SHV server system based on the Intel 450NX PCIset. The system bus interface supports up to 4 Pentium II Xeon processors at 100 MHz. An additional bus mastering agent such as a cluster bridge can be supported at reduced frequencies. Two dedicated PCI Expander Bridges (PXBs) can be connected via the Expander Bus. Each PXB provides two independent 32-bit, 33 MHz PCI buses, with an option to link the two buses into a single 64-bit, 33 MHz bus. The Intel 450NX PCIset memory subsystem supports one or two memory cards. Each card is comprised of an RCG, a DRAM array, and two MUXs. The MIOC issues requests to the RCG components on each card to generate RAS#, CAS#, and WE# outputs to the DRAMs. The MUX components provide the datapath for the DRAM arrays. Up to 8 GB of memory in various configurations are supported.

Other capabilities of the Intel 450NX PCIset include:
• Full Pentium® II Xeon™ processor bus interface (36-bit address, 64-bit data) at 100 MHz.
• Support for two dedicated PCI expander bridges (PXBs) attached behind the system bus so as not to add additional electrical load to the system bus.
• Support for both internal and external system bus and I/O bus arbitration.

Supporting Devices
The Intel 450NX PCIset is designed to support the PIIX4E south bridge. The PIIX4E is a highly integrated mulit-functional component that supports the following capabilities:
• PCI Rev 2.1-compliant PCI-to-ISA Bridge with support for 33-MHz PCI operations
• Enhanced DMA controller
• 8259 Compatible Programmable Interrupt Controller
• System Timer functions
• Integrated IDE controller with Ultra DMA/33 support