What Is An IRQ?

IRQ is short for "Interrupt Request." Modern computer systems have two IRQ Controllers, and each controller has 8 IRQs for a total of 16 although only 15 are available for use. Numbered 0 – 15, IRQ channels are system resources assigned to hardware devices in your system (sound cards, video cards, etc.).

An IRQ channel allows a hardware device like a sound card to interrupt the work of your computer’s processor and get its attention so that it can get its work done. Once a hardware device is done with the processor, the communication terminates and the processor picks up where it left off.

Plug and Play operating systems like Windows 95 and 98 usually do a good job handing out IRQ channels to hardware devices with minimal problems and 99% of the time, you will not have to worry about configuring IRQ channels by hand. Thank God.

But occasionally conflicts do arise with frustrating and debilitating results, especially when you have a lot of hardware in your computer. All modern computers have only 15 IRQ channels available to hand out to all the various hardware devices in your system and typically NO two devices can have the same IRQ although there are some exceptions. What’s more, several of the IRQs in your system are reserved for motherboard components like your hard drive controllers and system clock reducing the total pool available.

Typically IRQ conflicts only arise when you are adding a great deal of add-on cards to your system and are running low on IRQs or you are installing a new hardware device that absolutely insists on using an IRQ channel that has already been assigned to another hardware device and both end up with it.

If two devices end up with the same IRQ assigned to them, both devices may be disabled. If either of these two devices is critical to your system’s operation (like a video card), you system may fail to start normally and you may have to boot into safe mode.

Under Windows 95 / 98:

• Choose Start, Settings, Control Panel
• Double click the System icon
• Choose the Hardware tab
• Click your right mouse button on My Computer (at the top of the list)
• Choose Properties

Under Windows NT:

• Choose START, PROGRAM FILES, ADMINISTRATIVE TOOLS
• Choose Windows NT Diagnostics
• Click the Resources tab

These are the most common IRQ assignments in today's PCs.  Check yours to see if they match up.  In many cases, your assignments may be different depending on what kind of hardware you have in your system