192 If Something Goes Wrong
Resolving a hardware conflict
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Resolving hardware conflicts on your own
Computer components need resources to accomplish a task.
A device, such as a disk drive or a modem, needs a channel to
the computer’s Central Processing Unit (CPU). It also needs a
direct channel to the computer’s memory to store information
as it works. These channels of communication are commonly
referred to as system resources.
Interrupt Request Channel
The channel to the CPU is called an Interrupt Request (IRQ)
because it interrupts what the processor is doing and requests
some of the processor’s time. If two or more devices use the
same IRQ, the processor does not know which device is
asking for attention. This causes a hardware conflict.
Direct Memory Access
Similarly, the data required by the device is stored in a
specific place or address in memory called the Direct
Memory Access (DMA). The DMA provides a dedicated
channel for adapter cards to bypass the microprocessor and
access memory directly. If two or more devices use the same
DMA, the data required by one device overwrites the data
required by the other causing a hardware conflict.
Plug and Play
With Plug and Play and the operating system, avoiding
hardware conflicts is easy. Plug and Play is a computer
standard that helps the system BIOS (basic input/output
system) and the operating system to automatically assign
system resources to Plug and Play-compliant devices. In
theory, if every device connected to the computer is Plug and
Play-compliant, no two devices will compete for the same
system resources. Plug in the device and turn on your
computer. The operating system is automatically set up to
accommodate the new device.