Philips PCL304 - Processor; Memory; Ram

2-2
2.2.1 Processor
The
central
processing
unit
consists
out
of
a
80C386SX
mi-
croprocessor
and
an
optional
80C387SX
numeric
coproces-
sor.
:
The
800386
generates
24
address
bits
and
16
data
bits.
The
24
address
bits
are
generated
by
23
dedicated
address
lines
A1
-
A23,
with
AO
being
derived
from
the
mic-
roprocessor
byte
low
enable
signal.
The
80C386SxX
instruc-
tion
set
is
a
superset
of
the
8086/8088
and
also
includes
the
instruction
set
of
the
80186.
The
80C386SxX
is
object
code
compatible
with
the
8086,
80286
and
80386
microprocessor.
2.2.2 Memory
The
80C386SX
has
a
physical
address
space
of
16
Mbytes
in
protected
mode
and
of
1
Mbyte
in
real
mode.
Figure
XXX
shows
how
this
address
space
is
utilized.
The
protected
mode
additional
address
space
is
a
continuation
of
the
real
mode
address
space
with
one
exception,
the
BIOS
ROM
is
present
at
the
top
of
the
16
Mbyte
address
space
(it
has
two
locations
in
protected
mode).
2.2.3 RAM
The notebook can carry up to 5MB RAM internally, which is
most sufficient memory to run the most demanding applica-
tions or to use the most powerful operating systems.
The notebook mainboard is socketed for one SIMM (Single
In line Memory Modules), which can hold 2MB or 4 MB of
memory.
The on board standard 1MB RAM can be expanded to 3 or
5MB.
On board
Addressable Memory Space
16 Mb FFFFFFR
Max. of 15 Mbytes of
extended memory via
expansion slot
5 Mb 800000h
Max. on-board
extended memory
of 4 Mbytes
System BIOS
VGA BIOS
896 kb
Reserved for
extension ROM
768 kb
Reserved for
video RAM
640 kb
Conventional memory
000000h
Fig. 2-1
CS 55 799
10000 ----
OAQO00h ----
Mox. of 4 Mbytes of
an-beard
expanded memory
shadaw memo
shadow mema
shadaw memo
MDA.03039
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