SYSTEM EXPANSION
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Direct memory access (DMA) channel
Some hardware devices can use a DMA channel to access system
memory without directly burdening the processor. Computers have
DMA channels numbered DMA0 to DMA7.
The following table lists the DMA channels used by the computer
and shows which are available for use by expansion cards.
DMA Default assignment Available?
DMA0 Yes
DMA1 8-bit Audio Optionally
DMA2 Diskette/floppy disk controller No
DMA3 Enhanced Capabilities Port (default) Optionally
DMA4 System No
DMA5 16-bit Audio Optionally
DMA6 Yes
DMA7 Yes
Base input/output (I/O) port address
I/O ports are an area of ‘address space’ used by the processor to
communicate with hardware devices.
Some expansion cards are also controlled by I/O ports. The base
I/O port address specifies where the card’s ports begin. The
following table lists the I/O ports used by devices on the
motherboard.
Any ports not listed are available for expansion cards.
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