done before installing the card in the computer.
Other cards can be configured by running a
configuration program after installing the card. Some
cards use a mixture of both methods.
Cards often come with pre-configured or default
settings. It is best to rely on these settings as much as
possible, and change them only if they conflict with
ISA Interrupt request level (IRQ)
The "interrupt request level" or "IRQ" is the means
by which the expansion card sends a signal to get the
attention of, or interrupt, the processor. Your PC has
interrupt levels numbered IRQ0 to IRQ15, many of
which are needed for components on the computer's
motherboard. There are two ways round this.
Many motherboard components are Plug and
Play (PnP) devices. If you use BIOS Setup to
exclude or reserve an interrupt that is usually
assigned to one of these devices, an alternative
interrupt will be assigned through Plug and Play
and the original interrupt can instead be used by
the expansion card.
You can disable some motherboard components
either by means of the BIOS Setup utility or else
motherboard. This frees the resources used by
See the BIOS Setup & POST chapter for more
information about BIOS Setup. See the appropriate
Motherboard Features & Upgrades chapter for more
information about jumper settings and the usual
assignment of interrupts to motherboard components.
Direct memory access (DMA) channel
Some hardware devices can use a "DMA channel" to
access system memory without directly burdening the
processor. Your PC has DMA channels numbered
DMA0 to DMA7. As with interrupts, you can use
vacant channels or re-assign existing ones.
See the appropriate Motherboard Features & Upgrades
chapter for more information about the usual
assignment of DMA channels.
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