Specifications

Computer Architecture and Maintenance (G-Scheme-2014)
1) Conventional memory
2) Upper memory area
3) High memory area
4) Extended memory
5) Expanded memory
6) Video & RAM area
7) Adapter and special purpose ROM
8) Motherboard BIOS ROM.
Conventional or Base
memory: The original PC-
XT type system was
designed to use 1MB of
memory space in RAM.
This 1MB of RAM is
divided into several
sections, some of which
have special use.
Conventional memory is
the memory area within
first 1MB of system
memory that can be used
by DOS or application
software. DOS can read
write to the entire
megabyte but can manage
loading of program only
in the portion of RAM
space called Conventional Memory, which at the first PC was introduced was 512K.
The other 512K was reserved for the use by the system itself including the mother
board and adapter boards plugged into the system slots.
IBM decided after introducing the system in that only 384K was needed for the
reserved uses , and company began marketing PCs with 640K of users memory. Thus
640K became the standard for memory that can be used by the DOS for running the
program and is often called as memory barrier.
First 640KB becomes the standard memory that can be used by DOS for running
programs. This is also called as the base memory. After 640 K, some area is reserved
for the use of graphics boards, other adapters and ROM BIOS of motherboard.
Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)
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EX T EN D ED
Memo r y
M oth er B oard
RO M B I OS
EM S
win d ow
Ad ap ter RO M
Vid eo RAM
EX P AN D ED
m emo ry
Di vide d into
Log ic al Pa g es
an d
M ap ped in to
the E M S w i nd o
4-16K pa ges (64 K )
of "b an k sw itched "
memo ry ap pe ar in th e
EM S w ind ow u s ua lly
at sege m nt D OO O
Conetio na l
(B a se)
M em or y
32 M
OK
Ok
51 2k
768K
64 0K
83 2K
89 6K
1M
16 M/4 G