IRQ's are basically “stop and do this” messages given to the CPU when a device calls on the CPU to complete a task. For example, each time you press the Enter key on the keyboard, the keyboard controller sends an IRQ instruction to the CPU demanding it to carry out that function.
Each component in a computer must be configured to use its own communicaton line or IRQ setting for the successful transmission of data.
Some hardware devices share interrupt requests peacefully within a Windows system. If two devices are configured to use the same interrupt request conflicts will occur often resulting in neither of the hardware devices working.
The following table summarizes the most popular IRQ settings and the devices they are in charge of.
||Some video cards
||Floppy Drive Controller
||LPT1 (Printer Port)
||Redirected to COM2,
Power Management / ACPI Controller Function.
||Serial Bus Controller
||Hard drive controller
||USB Host Controller
||Hard Disk IDE Controller or
USB Host Controller
Wireless Network Controller
Television Tuner Card, or
Video Capture Device
||Audio Controller or
USB Enhanced Host Controller
|Table 1.1 - Various IRQ settings in a PC and the devices they control.
Many operating systems have utilities that allow you to check the IRQ settings for your computer. If you are running DOS, MSD (Microsoft Diagnostics) is the program you need to use to view information about the configuration of your computer. In Windows XP the System Information tool can provide you with extensive information about the hardware in your computer.