PC Serial Ports
Selecting an Add-On Serial Port
Card
This section presents advice on how to choose an
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.