A d d i n g E x p a n s i o n C a r d s

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.

APRICOT 340 OWNER’S HANDBOOK 6/5