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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.
♦
You can disable certain motherboard components either by
means of the BIOS Setup utility or else by changing jumper
settings on the motherboard. This frees the resources used by
those components.
♦
The audio system, USB controller and standard input/output
controller (e.g., for serial and parallel ports) are Plug and Play
(PnP) devices. If you use BIOS Setup or Windows 95 Control
Panel to exclude or reserve an interrupt that is usually assigned
to one of these devices an alternative interrupt will be assigned
though Plug and Play and the original interrupt can instead be
used by the expansion card.
See the BIOS Setup & POST chapter for more information about
BIOS Setup. See the 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 Motherboard Features & Upgrades chapter for more
information about the usual assignment of DMA channels.
Base input/output (I/O) port address
I/O ports are used by the processor to communicate with hardware
devices. Each port appears to the processor as an address low down
in its address space. Some expansion cards are also controlled by I/O
ports. The "base I/O port address" specifies where the card's ports
begin.
E x p a n s i o n C a r d s
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