Toshiba A205 - Manual (Page 161)

161 If Something Goes Wrong
Resolving a hardware conflict
The recommended procedure for getting multiple devices to work
together is to add and set up one device at a time. After you add
each device, test it to make sure it and all previously connected
devices work.
The device most recently connected to the system is the one most
likely to be causing a hardware conflict.
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
The data required by a 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.
If you install an older (legacy) device that the operating system
cannot recognize, the operating system may have difficulty
assigning resources to it. As a result, a hardware conflict can occur.