Microsoft KB Archive/72178

{| = Worksheet Recalculates Slowly in Excel 3.00 =
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Last reviewed: November 2, 1994

Article ID: Q72178

SUMMARY
Microsoft Excel 3.00 recalculates differently than Excel 2.x. The differences might cause Excel 3.00 to calculate more slowly than Excel 2.x.

Steps to Reproduce Problem
 Type a value into cell A1. In cell A2, place the formula =A1. From the Formula menu, choose Goto and type A2:A3500 in the Reference box. From the Formula menu, choose Fill Down. In cell A3500, you will have =A3499.  In cell B1 (or any cell not in the calculation), type =SUM(A1:A3500)  Change the value in A1.

The worksheet will be recalculated. In Excel 2.x, this calculation takes a very short time (less than a second). In Excel 3.00, it takes over a minute even though there are no links in the worksheet. The difference in speed exists because Excel 2.x always calculates the entire worksheet when a value is changed. Excel 3.00 calculates only those cells that are affected by values that have been changed. In the example above, when the value in cell A1 is changed, Excel first tries to calculate the SUM formula in cell B1. When it tries to add cell A2, it can't because A2 has not yet been calculated. So it calculates A2 and then attempts the SUM formula again. This time it is unsuccessful because A3 has not yet been calculated. This continues down the worksheet until 3499 attempts have been made and then the SUM is successful.

Workaround
Entering the SUM formula into cell B1 before entering and filling down the formula in column A will cause Excel 3.00 to calculate as quickly as Excel 2.x.