Number of Available Asynchronous Ports (98401)

The information in this article applies to:

Microsoft Windows NT Server 3.1
Microsoft Windows NT Workstation 3.1

This article was previously published under Q98401

SUMMARY

Windows NT does not have the same limit on asynchronous ports that Windows 3.1 has. This information was taken from the Windows NT source module, SERIAL.H:

   // 
   // Up to 16 Ports Per card.  However for sixteen
   // port cards the interrupt status register must me
   // the indexing kind rather then the bitmask kind.
   // 
   // 
   #define SERIAL_MAX_PORTS_INDEXED (16)
   #define SERIAL_MAX_PORTS_NONINDEXED (8)

MORE INFORMATION

For the standard ISA communications ports, each serial port must have its own interrupt. Otherwise, it depends on the driver. Because COM1 and COM3, and COM2 and COM4 typically share the same interrupts, only COM1 and COM2 are supported. However, the eight port multiport board can share the interrupt because there is only one device generating the interrupt.

Modification Type:	Major	Last Reviewed:	12/15/2003
Keywords:	kbHardware KB98401