Intel Xeon chipsets

Around the time that the Pentium III processor was introduced, Intel's Xeon line diverged from its line of desktop processors, which at the time was using the Pentium branding.

The divergence was implemented by using different sockets; since then, the sockets for Xeon chips have tended to remain constant across several generations of implementation.

The chipsets contain a 'memory controller hub' and an 'I/O controller hub', which tend to be called 'north bridge' and 'south bridge' respectively. The memory controller hub connects to the processors, memory, high-speed I/O such as PCI Express, and to the I/O controller hub by a proprietary link. The I/O controller hub on the other hand, connects to lower-speed I/O, such as hard discs, PCI slots, USB and Ethernet.

Intel's initial preferred chipset for Pentium III Xeon was the 840.

The Pentium III Xeon bus protocol allowed four processors on the same bus, so the 440GX AGPset could be used in four-CPU systems; the limit of 2GB of main memory remained. These support Slot 2.

There was also the 450NX PCIset, which consisted of several chips: a single 82451NX Memory and IO Bridge Controller roughly analogous to the North Bridge, up to two 82454NX PCI Expander Bridges which converted the protocol used by 451NX to two 32-bit PCI33 or one 64-bit PCI33 bus, along with up to two memory cards each equipped with one 82452NX RAS/CAS Generator chip and two 82453NX Data Path Multiplexer chips. It supported PIIX3 and PIIX4E south bridges, and EDO DRAM.

In August 1999 Intel began shipping the Profusion PCIset. The chipset was based on technology developed by the Corollary company, which Intel acquired. It supported up to 8 Pentium III Xeon processors on two busses and maintained cache coherency between them. Profusion supported up to 32 GB of memory. It saw some limited competition from the NEC Aqua II chipset. Another minor player in the eight-way space was Axil Computer's NX801, which was used in an 8-way (two buses) Pentium Pro design, commercialized by Data General as their AV-8600 computer.

E7500 corresponded to the first Northwood-based Pentium4 Xeons, E7501 is essentially identical but supports faster FSB and memory. The E7320, E7520 and E7525 chipsets correspond to Prescott-based Pentium4 Xeons, and differ mainly in their PCI Express support. These support Socket 604.

Note that the 82870P2 chips mentioned above were initially designed for the Intel 870 chipset for Itanium 2, and that the summary page of the E7320 datasheet incorrectly claims three PCI Express interfaces.

These chipsets use a 'dual independent bus' design, in which each socket has its own connection to the chipset. These support LGA 771.

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