IBM Personal System/2 50 - System Memory Maps

The
timing
of
the
memory
signals
on
the
Type
2
system
board
with
85-nanosecond
memory
installed
is
similar
to
the
Hitachi
HM51256CP-8,
85-nanosecond
DRAM
or
equivalent.
The
timing
of
the
memory
signals
on
the
Type
2
system
board
with
120-nanosecond
memory
installed
is
similar
to
the
Hitachi
HM51256CP-12,
120-nanosecond
DRAM
or
equivalent.
System Memory Maps
The
following
figure
shows
the
mapping
of
the
memory
locations
on
the
Model
50.
A
256-byte
portion
of
this
RAM
is
reserved
as
a
BIOS
data
area.
A
1KB
portion
of
this
RAM
is
reserved
as
an
extended
BIOS
data
area.
See
the
/BM
Personal
System/2
and
Personal
Computer
BIOS
Interface
Technical
Reference
for
details.
Hex Range Function
000000
to
O9FFFF
640KB
System
Board
RAM
*
0A0000
to
OBFFFF
128KB
Video
RAM
0C0000
to
ODFFFF
128KB
I/O
Expansion
ROM
OE0000
to
OFFFFF
128KB
System
Board
ROM
100000
to
15FFFF
384KB
System
Board
RAM
160000
to
FDFFFF
Channel
Expansion
Memory
Addresses
FE0000
to
FFFFFF
128KB
System
Board
ROM
*
With
the
system
board
in
the
setup
mode,
the
system
board
memory
can
be
disabled
through
System
Board
POS
Register
3
(see
page
2-9).
Figure
3-4.
System
Memory
Map
3-8
Model
50
System
Board
—
October
1990