Processors
Intel® Pentium® II Xeon® Processor
Integration Notes

Updated January 1999

This overview is for professional system integrators building workstations and mid range and higher servers with Intel® Pentium® II Xeon® processors and industry-accepted motherboards, chassis, and peripherals.


Pentium II Xeon Processor Features
The Pentium II Xeon at 400 MHz processor is Intel’s first member of the new Intel Inside microprocessor family designed exclusively for today’s powerful servers and workstations. The Pentium II Xeon 450MHz processor is Intel’s second member. Building on the architecture of the Pentium II processor, the Pentium II Xeon processor adds the superior performance, manageability, and mission-critical reliability that your Intel-based servers and workstations demand.

The Pentium II Xeon processor delivers industry leading performance from its larger and faster Level 2 (L2) caches, multiprocessing capabilities, and a 100 MHz system bus. Systems based on the Pentium II Xeon processor are scalable, with support for:
  • Up to four processors using "glueless" multiprocessing capabilities
  • Eight-way and above systems using clustering technologies like NUMA and VI architecture
  • Greater than 4 GB of memory using expanded 36-bit addressing

Key features of the Pentium II Xeon processor include:
  • 0.25 micron P6 microarchitecture core operating at 450 MHz and 400 MHz
  • Dynamic Execution
  • 400 MHZ offers 1 MB or 512 KB L2 cache options.
  • 450 MHZ offers 2 MB, 1 MB, or 512 KB L2 cache options.
  • L2 cache bus operating at the same speed as the processor core
  • New system management features via the System Management Bus (SMBus)

Boxed Pentium II Xeon Processor Contents
  • 450 MHz processor with 2 MB, 1 MB, or 512 KB L2 cache or 400 MHz processor with 512 KB or 1MB L2 cache
  • Attached Passive Heatsink
  • Installation Manual
  • Certificate of Authenticity
  • Intel Inside® Logo Sticker
  • 3-year Limited Warranty

Motherboard Selection
Motherboards used with the Pentium II Xeon processors at 450 MHz and 400 MHz must meet Intel’s published processor specifications.

Motherboards used with the Pentium II Xeon processor 400 MHz must support a 100 MHz system bus. Motherboards based on Intel’s 82440GX and 82450NX chipsets support a 100 MHz system bus. Intel offers two boxed platforms (motherboard and chassis) combinations for system integrators building Pentium II Xeon processor systems: the MS440GX and the SC450NX.

NOTE: B0-step versions of the Pentium II Xeon processor 400 MHz and B1-step versions of the boxed Pentium II Xeon processor 450 MHz should be used only in 82440GX based systems. To distinguish between processor steppings, see How to Match Processor Steppings which lists processor steppings and their test specifications.

Chassis Selection
Selection of a proper chassis is a very important consideration - particularly to ensure that proper venting and good airflow are present so that the processor does not exceed its thermal limits.

Integrators are encouraged to choose a chassis that will allow them to meet the thermal requirements of the processor. For assured compatibility, Intel’s two boxed motherboards supporting the Pentium II Xeon processor, the MS440GX and SC450NX, can be purchased complete with a chassis that will accommodate the motherboard.

Processor Connector Requirements
Motherboards supporting the Pentium II Xeon processor feature a 330-contact slot connector (previously called Slot 2) into which the processor is inserted. Processors using a 330-contact slot connector permit a closely coupled, high speed L2 cache, high-frequency signal integrity, and headroom for processor technology evolution.

Motherboards using a Pentium II Xeon processor require a mechanical support for the processor called a retention mechanism. The retention mechanism holds the processor securely in the 330-contact slot connector and protects the processor and motherboard from damage. Motherboards with a dual processor design typically require a dual retention mechanism. The single or dual retention mechanism is not included with the Boxed Pentium II Xeon processor. The single or dual retention mechanism should be provided, along with installation instructions, by your motherboard supplier. (All Intel boxed motherboards that support the 330-contact slot connector include an appropriate retention mechanism.) Figure 1 shows a second processor being installed in a dual retention mechanism.

Install into a Dual Retention Mechanism


Figure 1.
Second Pentium II Xeon Processor and Heatsink Being Installed into a Dual Retention Mechanism


Voltage Requirements
The Pentium II Xeon processor core and L2 cache operate at different voltages. In order to support these different voltages the processor contains five voltage identification pins for the core and five for the L2 cache. The core and L2 cache are specified to operate at the following voltages:

Processor Frequency L2 Cache Size Processor Core Voltage L2 Cache Voltage Voltage Tolerance
400/512KB 2.0 V 2.5 V +/- 0.085 V
400/1MB 2.0 V 2.5 V +/- 0.085 V
450/512KB 2.0 V 2.7 V +/- 0.085 V
450/1 MB 2.0 V 2.7 V +/- 0.085 V
450/2 MB 2.0 V 2.7 V +/- 0.085 V


Proper voltage must be supplied for reliable operation. It may be supplied by a regulator(s) integrated in the motherboard or by a voltage regulator module (VRM) installed on the motherboard in a VRM header. Intel strongly recommends the use of the VRM header that meets the VRM 8.3 specification.

If the regulator is integrated in the motherboard, it must be Voltage ID (VID) programmable to allow the processor to program the correct voltage during power-on.

If the motherboard has a VRM 8.3 header, then a VRM must be installed in the header to power the associated processor (core and L2 cache). Most VRMs are VID-programmable. If your motherboard has a fixed-voltage VRM, its output voltage must match the processor requirements.

Since the operating voltage of Pentium II Xeon processors (both core and L2 cache) may be changed as the processor goes through stepping changes, VID-programmable voltage regulators are the preferred solution.

Thermal Management Considerations
The table below shows the maximum operating temperatures for Pentium II Xeon processors, measured at the center of the processor's thermal plate beneath the heatsink:

Processor Frequency and L2 Cache Size Processor Stepping Max. Operating Temp. in °C Total Max Processor Power in Watts
400/512KB B0/B1 75 30.8
400/1MB B0/B1 75 38.1
450/512KB B1 75 34.5
450/1 MB B1 75 42.8
450/2 MB B1 75 46.7


You must use a chassis that provides sufficient airflow to keep the processor under its maximum operating temperature in the warmest user environment. Running the processor above its maximum temperature specification will void the warranty and can lead to functional and performance degradation. Intel recommends the use of ATX 2.01-compliant motherboards and chassis for proper mechanical fit. The combination of the heatsink shipped with the Boxed Pentium II Xeon processor, an ATX form-factor motherboard and an ATX 2.01-compliant chassis can be a good thermal management solution. Be aware that the airflow in non-ATX 2.01-compliant chassis varies significantly - depending on venting, internal brackets and other factors. Chassis with low airflow can cause processors to run warmer than their maximum specification. Thermal evaluation should always be performed when selecting a chassis for Pentium II Xeon processor-based systems. Refer to Thermal Management for Pentium® II Xeon® Processor-Based PCs for more information.

BIOS Considerations
BIOS code on Pentium II Xeon processor-based motherboards contains data that is specific to a processor silicon stepping. (A silicon stepping is a specific revision of the silicon.) You must ensure that this stepping data matches the processor stepping used. When the stepping data doesn't match the processor stepping, you must update the data before shipping the system.

Motherboard vendors can supply information about the default stepping of the Pentium II Xeon processor supported by the BIOS on a specific motherboard. If the default stepping data does not match the processor stepping used, the motherboard vendor can supply a system BIOS upgrade for the motherboard. Make sure to specify the processor speed and stepping that you are currently using.

Dual and Multiple Processor System Considerations
In addition to single-processor use, the Pentium II Xeon processor is designed for dual and multiprocessor operation.

Pentium II Xeon processors are tested during manufacturing to ensure they will work in configurations with multiple processors of the same speed and same L2 cache sizes. While operation with different speed processors and different L2 cache sizes is not prohibited, it is not tested by Intel and could have implications when running with operating systems that support multiprocessing.

Intel tests dual processor configurations with different steppings of the Pentium II processor as new processor steppings are introduced. Certain Pentium II Xeon processors of the same speed but different steppings can be mixed in dual processor configurations, provided that the motherboard's BIOS will support this option. For more information, see Mixing Processor Steppings and Speeds below.

NOTE: B0-step versions of the Pentium II Xeon processor 400 MHz and B1-step versions of the boxed Pentium II Xeon processor 450 MHz should be used only in 82440GX based systems. To distinguish between processor steppings, see How to Match Processor Steppings which lists processor steppings and their test specifications.

Recommendations for Integration of Dual and Multiprocessor Systems:

  1. Ship multiprocessor systems with all processor slots populated to ensure that processor speeds, steppings, and L2 cache sizes are the same. When partially populated systems are shipped, customers attempting to install additional processors may have difficulty locating them with the same stepping or cache sizes. In these cases, they may have to replace the original processor to obtain a system with processors of the same stepping.

  2. Make sure that the correct motherboard BIOS is loaded into both processors. Contact your motherboard vendor if you have any questions on BIOS upgrades.

  3. If a system is shipped without all processors installed, test the system first with all processor slots populated. This will demonstrate whether the motherboard supports multiprocessor operation. You should also provide these customers with speed and stepping information for the original processor. This will ensure they understand the importance of having processors of the same speed, stepping, and cache size. It also warns them of the risk of having to replace the original processor in the future if earlier stepping processors are not available.

  4. If a system is shipped without all processors, install the operating system with all processors installed. Some operating systems will install different kernel versions, depending on the number of processors present. Once the operating system has been installed the remaining processors can be removed before system shipment. This alleviates the need to reinstall the operating system if more processors are added later. Make sure to populate all open processor connectors with appropriate termination cards which should have been supplied with your motherboard.

  5. Integrators thinking about mixing processor steppings within a multi-processor system should first read Mixing Processor Steppings and Speeds for an overview of the issues involved.


How to Match Processor Steppings
The easiest way to match steppings is to compare the 5-character test specification numbers on the top of Pentium II Xeon processors. The number starts with an "S" and is followed by 4 characters (for example, "SL2RH"). Boxed Pentium II Xeon processors have the test specification number also printed on the package label.

Identical silicon steppings may sometimes be shipped with different test specification numbers—depending on whether they are for OEMs or for system integrators. The following table shows comparisons of the two types of numbers (at this time there are no test specification differences to report). Some Intel boxed processors may have OEM test specification numbers.

Boxed Pentium II Xeon Processor Silicon Test Specification vs. OEM Test Specification
This information has been moved. See the Processor S-spec Table for detailed information.


Mixing Processor Steppings and Speeds
Though Intel recommends using identical steppings of processor silicon in multiprocessor systems whenever possible (as this is the only configuration which receives Intel's full testing), Intel supports mixing processor steppings and does not actively prevent various steppings of the Pentium II Xeon processor from working together in multiprocessor systems. However, since Intel cannot test every possible combination of devices, each new stepping of a device is fully tested only against the latest steppings of other processors and chipset components. For more details on mixing processor steppings in multiprocessor systems, see the Pentium II Xeon® Processor Specification Update.

The following list explains the known issues with mixing steppings:
  • In mixed stepping configurations, all processors must be run at an identical frequency and must have the same L2 cache sizes

  • The workarounds for various errata must take all processors into account. Errata for the Pentium II Xeon processor are published in the Pentium® II Xeon® Processor Specification Update.

  • Errata for all processor steppings present in a system will affect that system, unless worked around.

  • Some operating systems may not support full functionality when processors with mixed steppings are present. Check with your operating system vendor for details.

    Due to the variety of motherboard vendors in the market and the number of system BIOS revisions, some system-level issues may occur that lie outside the realm of any mixed stepping evaluation performed by Intel. Recommendations for shipping systems that mix Pentium II Xeon processor steppings are as follows:

  • Choose a motherboard vendor with a history of quality and dual and multiprocessor experience to minimize potential system-level issues

  • Contact your motherboard vendor for information on mixed stepping validation performed on your particular dual or multiprocessor motherboard

  • Make sure that the motherboard’s BIOS will support all processor steppings. As indicated in BIOS Considerations above, motherboard vendors should be able to supply information about the steppings of the Pentium II Xeon processor supported by the BIOS on a specific motherboard.

  • Refer to the Pentium® II Xeon® Processor Specification Update for information on processor errata, their workarounds and potential performance issues before integrating dual and multiprocessor systems. The specification update (order number: 243776-xxx) can be obtained from Intel literature at 1-800-548-4725. The order number changes with each specification update; the -xxx numbers grow larger with each revision. Choose the highest revision number to receive the latest update.

Information about mixing processors of different speeds can be found in the Pentium® II Xeon® processor at 400 and 450 MHz Datasheet.

Additional information related to stepping, voltage and packaging of each specific Pentium II Xeon processor can be found in the Pentium® II Xeon® Product Specifications and Comparisons.

This applies to:

Intel® Pentium® II Xeon® Processor



Solution ID: CS-023499
Last Modified: 24-May-2010
Date Created: 16-Oct-2006
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