Absolute Beginner's Guide to A+ Certification

Hardware Resources

There are four types of hardware resources used by both onboard and add-on card devices:

• IRQ

• I/O port address

• DMA channel

• Memory address

Each device needs its own set of hardware resources, or needs to be a device that can share IRQs (the only one of the four resources that can be shared). Resource conflicts between devices can prevent your system from starting, lock up your system, or even cause data loss.

IRQs

IRQs, or interrupt requests, are a series of 8 or 16 lines that run between the CPU and both built-in and expansion card devices. Most devices use at least one IRQ. As the name implies, IRQs enable devices to interrupt the CPU to signal for attention when they need to send or receive data. Without IRQs, the CPU would run ...