CertiGuide to A+ (A+ 4 Real)  9  Chapter 8: Motherboards

What is Interrupting? 1 DMA

IRQ stands for Interrupt Request. This is a specialized signal from a hardware device such as a keyboard or network card stating that it requires the CPU’s attention. Each device is assigned a specific IRQ channel for such requests so the CPU can keep track of which device is making the request. As you have read previously, it is now common for more than one device to share an IRQ however; they cannot use the same channel to communicate with the CPU at the same time. This would result in a resource conflict and at least one of the devices would stop working.

On a Windows XP machine, to see the information regarding which IRQ and other resources a device such as a modem is using, you need to do the following. Click on Start -> right-click My Computer -> click on Properties -> click on the Hardware tab -> click on the Device Manager button -> click on the “plus” (+) sign next to Modems -> right-click the name of the modem -> click on Properties. The modem’s Properties box will open. Click on the Resources tab. You will see information on the specific memory range; I/O and IRQ used by the device and will see if there is any indication of a conflict. Usually, there will be a message stating “No conflicts”. If you go back to the Device Manager box and click on View, you can change the preference from Devices by type to Resources by type to see resources by their categories. If you expand the “plus” (+) sign next to IRQ, you will see a list of devices by their expansion bus (usually ISA and PCI) and display which IRQ channels each one uses.

What is Interrupting? 1 DMA