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Microsoft KB Archive/101467

From BetaArchive Wiki

How to Test for a Faulty Pentium FPU

The information in this article applies to:

  • Microsoft Excel for Windows, versions 4.0, 4.0a, 5.0, 5.0c


If you are using Microsoft Excel on a computer that contains an Intel Pentium processor, you may receive unexpected results when you perform mathematical operations that involve dividing certain combinations of numbers.


This problem is caused by an error in the FPU (floating point unit), a part of the Intel Pentium chip that performs elaborate calculations. Intel is aware of this problem.

To test if the FPU in the Pentium chip in your computer has this problem, use any of the following methods:

Method 1: Using the Windows Calculator located in the Accessories group in

Program Manager, do the following:

a. Enter the value 5505001. Press the division button (/).

b. Enter the value 294911. Press the equal sign button (=).

The correct answer is 18.66665197297. If you do not receive this value, for example if you receive the value 18.6660009291, your Pentium computer has a faulty FPU.

Method 2: Using a worksheet in Microsoft Excel, do the following:

a. On a new worksheet, enter the following:

A1: 1
A2: 3221224323
A3: =A1/A2
A4: =A3*A2

b. Select Column A. From the Format menu, choose Column, and then choose AutoFit Selection.

If the value returned in cell A4 is NOT 1, your Pentium computer has a faulty FPU.

Method 3: Obtain the Application Note "Pentium Floating Point Unit (FPU)

Patch" (WE1136). You can run the patch provided in this application note to determine whether or not your computer has this problem.

To Obtain the Pentium FPU Patch

The quickest way to obtain the Pentium FPU patch is to download it from the Microsoft Download Center. The size of the WE1136.EXE file is approximately 16K. If you are unable to download the patch, see the instructions for alternative ways to obtain it.

The following file is available for download from the Microsoft Download Center. Click the file name below to download the file:


For more information about how to download files from the Microsoft Download Center, please visit the Download Center at the following Web address

and then click How to use the Microsoft Download Center.

If you are unable to access the source(s) listed above, you can have this Application Note mailed or faxed to you by calling Microsoft Product Support Services Monday through Friday, 6:00 A.M. to 6:00 P.M. Pacific time at (425) 635-7070. If you are outside the United States, contact the Microsoft subsidiary for your area. To locate your subsidiary, see the Microsoft World Wide Offices Web site at:

NOTE: This patch will work on all international versions of Microsoft Excel for Windows.

For additional information, please see the following article(s) in the Microsoft Knowledge Base:

Q123783 : XL AppNOTE: "Pentium Floating Point Unit Patch"

Additional query words: 7.00 4.00a 5.00c

Keywords : xlwin
Version : 4.x 5.00 5.00a 7.00
Platform : WINDOWS
Issue type :
Technology :

Last Reviewed: December 10, 1999
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