User guide

OWNER’S HANDBOOK
4/4 Expansion Cards
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
DFFFFh – an area known as the upper memory block
or UMB. You can exclude or reserve UMB regions
with the BIOS Setup utility.
The card’s documentation should list its possible base
memory addresses. You may 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.
More about memory addresses
Memory addresses are always written in base 16 or
“hexadecimal” notation. Unlike the ten digits of the
decimal system (0-9), hexadecimal uses sixteen digits
(0-9 and A-F, where A=10, B=11, C=12 and so on up
to F=15).
Hexadecimal numbers are denoted either by the suffix
“h” or by the prefix “0x”. The final digit of a five-
digit memory address is often omitted, so C8000h
may be written as C800h.
Because amounts of memory are usually stated as
kilobytes (Kbytes) rather than in hexadecimal
notation, the following conversion table may be
helpful:
4 Kbytes = 1000h 32 Kbytes = 8000h
8 Kbytes = 2000h 64 Kbytes = 10000h
16 Kbytes = 4000h 128 Kbytes = 20000h