A+ Study Guide: CMOS

Most personal computers have 2 serial ports. The BIOS lets you assign COM1/COM2/COM3/COM4 to serial port 1 or 2. Most BIOS's also allow you to set the I/O addresses and IRQ but this is usually done automatically. The following are COM/Serial Port Settings in the Setup program:

• Integrated Serial Port 1/Serial Port 2
  This setting allows you to specify the resources for the first and second serial ports on the motherboard. The exact name used for the various options varies. It is sometimes called "COM1", "COM2", etc. while at times they just list the I/O address and IRQ options. You will find the following options for every serial port setting:

• 3F8/IRQ4 (COM1):
  This sets the serial port to the I/O address and IRQ normally used by COM1. This is usually the default setting for the first serial port.

• 2F8/IRQ3 (COM2):
  This sets the serial port to the I/O address and IRQ normally used by COM2. This is usually the default setting for the second serial port.

• 3E8/IRQ4 (COM3):
  This sets the serial port to the I/O address and IRQ normally used by COM3.

• 2E8/IRQ3 (COM4):
  This sets the serial port to the I/O address and IRQ normally used by COM4.

• (Other options):
  Some systems allow you to select other IRQ's to assign to the onboard ports to use, incase you are trying to avoid a resource conflict.

• Disabled:
  Disables the serial port.

Normally the first serial port is set to the resource settings for COM1, and the second to COM2.