A d d i n g E x p a n s i o n C a r d s
6/6 APRICOT LS/VS340 OWNER’S HANDBOOK
I/O ports
Default assignment
2F8h-2FFh
Serial port B
300h-301h
Audio: MIDI
330h-331h
Audio: MIDI (alternate)
378h-37Fh
Parallel port 1
388h-38Fh
Audio: FM synthesiser
3B0h-3BFh
Monochrome display and printer adapter
3B4h, 3B5h, 3BAh
Video subsystem
3C0h-3C5h
VGA
3C6h-3C9h
Video DAC
3CAh-3DFh
VGA
3F0h-3F7h
Diskette drive controller
3F8h-3FFh
Serial port A
Base memory address
Some expansion cards are fitted with memory of their own, usually
read-only memory (ROM) containing functional extensions to the
computer’s BIOS (basic input/output system) ROM. Some cards
also have random-access memory (RAM).
In order that this memory can be recognised by the system
processor, it must be mapped somewhere within the computer’s
own address space. By setting the
base memory address
you specify
where the card’s memory begins within the address space. Typically,
an expansion card’s memory must be mapped onto the addresses
between C8000h and EFFFFh.
The card’s documentation should list its possible base memory
addresses. You will also need to know how much memory the card
has, so that you can leave the right gap between this card’s base
address and the next. (Some cards allow you to specify the amount
of memory you want to map, but usually this is fixed.)
