Microsoft KB Archive/125759

= Windows NT3.5 Improves Performance with Intel Neptune PCI Chip =

Article ID: 125759

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Server 3.5

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This article was previously published under Q125759



SUMMARY
Microsoft has developed new Windows NT version 3.5 Hardware Abstraction Layer (HAL) Dynamic-Link Libraries (DLLs) that take advantage of Intel's new A1 stepping of their Neptune 82434 PCI Cache Memory Controller (PCMC) chip. These new DLLs allow your PCI-based computer with A1 or greater stepping to achieve full operating performance.



MORE INFORMATION
The A0 stepping of the Neptune 82434 PCMC chip had two routines, Read- Around-Write Enable and PCI-to-Memory Posting Enable, that did not function according to specification. This led to data corruption in random access files and occasionally in memory.

Because BIOS updates to correct this problem were generally unavailable at the time of its release, Windows NT version 3.5 avoided potential data corruption by disabling these routines. However, this workaround resulted in a slight performance degradation.

Intel has since introduced A1 stepping for their Neptune 82434 chip which resolves the data corruption problem. Consequently, Microsoft has modified Windows NT HAL to only disable these routines on A0 chips. Chips with A1 and greater steppings will function normally and achieve full operating performance.

The new HAL is available in the latest U.S. Service Pack for Windows NT version 3.5. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K

Additional query words: prodnt

Keywords: KB125759

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