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Selecting an Add-On Serial Port
Card
This section presents advice on how to choose an add-on serial port card for
use with the PassageWay Service Provider. Because the PassageWay
Service Provider does not have any unique requirements with respect to serial
ports, this advice applies generically to selecting a serial port for use with any
peripheral.
In general, there are two main things to consider when selecting a serial port
for use with the PassageWay Service Provider:
1. Choose a card that offers the flexibility to configure its serial port IRQs
to values other than IRQ3 and IRQ4 (for example, to IRQ2 or IRQ5).
This capability often proves to be very beneficial, especially if you are
purchasing the card to add a COM3 and/or COM4 port to your
system. As was described at length in "Workarounds and Solutions to
the IRQ Conflict Problem," for PCs that do not support IRQ sharing
(which includes most PCs, unfortunately), the ability to relocate the
IRQ for COM3 or COM4 away from the defaults (IRQ4 and IRQ3,
respectively) represents the only direct solution to conflicts that may
arise when attempting to use COM1 along with COM3 or COM2 along
with COM4 under Windows.
If you know that your PC does not support IRQ sharing, or if you are
not sure, it is a good idea to purchase a card with this capability. If
you know that your PC supports IRQ sharing, this capability is not as
potentially important.