I have a Clarion Database Developer for DOS 3 application that
calls a C function that sends a BELL character to an external
cash drawer to pop it open.  The client who was using this
point-of-sale program upgraded their computer from a 486 to
a Pentium and now the cash drawer does not open.

Could it be that the UART on the Pentium serial port is too
fast for the cash drawer?  Could there be a software reason
for the failure?