Microsoft KB Archive/184101

= Very Small Single and Double-Precision Values Are Rounded to Zero on Alpha Computers =

Article ID: 184101

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition

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This article was previously published under Q184101





SYMPTOMS
Very small single-precision values (values less than 1.175e-38) and very small double-precision values (values less than 2.225e-308) are always rounded towards zero (chopped,) even when the rounding mode is set to round to nearest or round towards plus or minus infinity.

You can test for the presence of this problem by checking to see if the double-precision value 1.4e-44 is converted to the single-precision value of 1.4e-44, but the double-precision value 1.4e-45 is converted to single- precision value of zero.



CAUSE
This problem is caused by inaccurate rounding in the software emulation of these very small values. This problem should not be confused with normal Alpha hardware performance, which rounds ALL very small values to zero. For information about these very small values, please search the RISC Programmer's Guide (available in the online documentation in Microsoft Visual C++ for Alpha) for topics on denormals.



RESOLUTION
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack



STATUS
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

Keywords: kbbug kbfix KB184101

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