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Expansion card memory
Some expansion cards are fitted with ROM. Typically
expansion card ROM contains extensions to the
motherboard BIOS providing additional functionality.
Expansion card ROM (sometimes known as slot ROM)
must be addressed somewhere in the processor's memory
map. An area of the memory map of an ISA compatible PC
is allocated for expansion card ROM.
If you are unfamiliar with the concept of memory maps, and
the hexadecimal numbering system the following text
attempts to explain them. If you are familiar with the
memory map of an ISA PC then continue to Memory
configuration .
Numbers and computers
For a variety of reasons, in computer literature and
terminology, numbers are sometimes in hexadecimal
notation rather than the decimal that we are all familiar with.
Hexadecimal is a long word and it is often shortened to
hex.
If you think of the decimal system using columns:
1000
(10x10x10)
The number 1019 is:
1000
1
Each time you add 1 to a column that contains 9 that
column goes back to 0 and you add 1 to the column to the
left. The columns represent powers of 10: 10x10, 10x10x10
and so on, and the decimal system is said to be base 10 .
The hex numbering system uses a base of 16. Hex
numbering works in exactly the same way as the decimal
system, except you must add 1 to a column that contains
15 before you add 1 to the column to the left.
100
10
(10x10)
(10)
100
10
0
1
1
(1)
1
9
57
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