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Adding Expansion Cards
APRICOT 340 OWNER’S HANDBOOK 6/5
Direct memory access (DMA) channel
Some hardware devices can use a DMA channel to access system
memory without directly burdening the processor. Your computer
has DMA channels numbered DMA0 to DMA7.
The following table lists the DMA channels used by the computer.
Channels which have no default assignment can be used by
expansion cards. Note that DMA3 is free if the parallel port is not
configured to ECP mode.
DMA Default assignment
DMA0 -
DMA1 8-bit audio (MS/LS models)
DMA2 Diskette/floppy disk controller
DMA3 Parallel port in Extended Capabilities Port mode
DMA4 System
DMA5 16-bit audio (MS/LS models)
DMA6 -
DMA7 -
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.
The table on the next page lists addresses used by devices on the
motherboard. Any ports between 100h and 3FFh that are not listed
below may be used by an expansion card.
Motherboard jumper settings determine which I/O ports are used
by the SoundBlaster-compatible audio system in Apricot MS340 and
LS340 models. See Appendix A, “Inside the System Unit”, for more
information.