Microsoft KB Archive/45070

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Symptoms of a Faulty Math Coprocessor in Microsoft Excel

The information in this article applies to:

  • Microsoft Excel for Windows, versions 2.x, 3.0, 4.0, 5.0


If the math coprocessor is faulty, you may receive some of the following symptoms (the numbers given are examples only; different numbers may appear than the ones used in these examples):

  • Column width: will add 10 to 20 more units and save that way.
  • Font sizes: Font size is carried out to multiple decimal places (for example, size 10 will be displayed as 9.3333 or 10.00781250000018).
  • Cell numbers: entering a whole number in a cell will show a decimal number added to it.
  • Help: When you click About on the Help menu, it will appear that your computer has ten times the memory that is possible for your computer to have.
  • Cell values: any values entered into a cell will appear as the same value. For example, if you enter 1, 2, 3 in different cells, all of the cells will display the value 8.
  • Unrecoverable Application Errors can occur when using Microsoft Excel with Microsoft Windows 3.0 and general protection (GP) faults can occur when you use using Microsoft Windows 3.1). In addition, the computer may stop responding (hang) when you change a cell width.
  • Choosing Page Setup from the File menu and pressing OK without making any changes causes a "Number is not valid" error message when you highlight one of the margin entries.

These symptoms may also occur in a system which has the wrong math coprocessor installed. The math coprocessor should be the same clock speed as the computer or one level faster. (For example, a 25 mhz computer should be able to function correctly with a 33 mhz coprocessor.) To test for this, turn off the turbo switch (if your computer has one). This will reduce the clock speed by half, which will effectively make the computer slower than the coprocessor. If the symptoms disappear, then the installed math coprocessor is most likely the wrong clock speed for the system.

If you have the symptoms noted above, you can also remove the math coprocessor and then restart Microsoft Excel. If the problem does not occur again, then the math coprocessor may be faulty.

Be sure to check the AUTOEXEC.BAT and CONFIG.SYS files for obvious items (TSRs), make sure the system BIOS version is current, and check to see if the coprocessor is properly seated.

Additional query words: font 1-409 format number incorrect

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Last Reviewed: March 15, 1999
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