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DMA channels
ISA compatible PCs are equipped with a seven channel
DMA (Direct Memory Access) controller. This DMA
subsystem allows peripherals to access motherboard
memory directly.
Without the DMA subsystem every memory access would
have to involve the processor. Using DMA, peripherals can
access memory without stopping the processor executing
its current task.
The table below lists the DMA channels available on the
motherboard and their default functions. The notes explain
whether the default function can be disabled, if so how, and
under what circumstances it is safe to do so.
DMA
Function
Note
channel
0
SLCD
Available if no SLCD CD-ROM
CD-ROM
drive is fitted and the SLCD interface is
interface
disabled in SETUP
1
Audio
Available if the audio system is disabled in SETUP
channel A
2
Floppy drive Always used by the
interface
motherboard
3
Audio
Available if the audio system is disabled in SETUP
channel B
5
not used
Available
6
Hard disk
Always used by motherboard
interface
7
not used
Available
Note
There is no DMA channel 4 on any ISA compatible system.
Refer to the table above, and the documentation supplied
with the card to establish which DMA channel, if any, to
use and how to select it.
