QuickBasic May Not Function with 25-MHz 80387 Coprocessor (39256)

SYMPTOMS

Customers have reported that QuickBasic version 4.5 does not function correctly with a 25-MHz 80387 math coprocessor chip. The reported problems include the following:

Incorrect floating-point numeric results
Coprocessor not detected

This problem does not occur on 80387 chips slower or faster than 25 MHz.

Microsoft has not tested QuickBasic version 4.5 with 25-MHz 80387 chips.

MORE INFORMATION

To test potential problems, you can compare numeric results with and without the coprocessor by turning on or off QuickBasic's access to the coprocessor. The following MS-DOS command turns off QuickBasic's access to the coprocessor in the current boot session (where any message with one or more characters must follow the equal sign [=]):

set NO87=Coprocessor is currently disabled.

The following command makes the coprocessor accessible again (where no characters follow the [=]):

   set NO87=

One customer reports that QuickBasic 4.5 didn't recognize a 25 MHz 80387 on an Atronics 386B motherboard. Microsoft has not confirmed this information.