IBM Personal System/2 65 SX User Manual

Bits
5,4
These
bits
indicate
the
operating
mode
of
the
display
attached
to
the
video
port,
as
shown
in
the
following
table.
Bits Display
54
Operating
Mode
00
Reserved
01
40-Column
Mode
10
80-Column
Mode
11
Monochrome
Mode
Figure
3-27.
Display-Operating-Mode
Bits
Bits
3,2
These
bits
are
reserved.
BiY1
When
set
to
1,
this
bit
indicates
that
a
math
coprocessor
is
installed.
Bit
0
When
set
to
1,
this
bit
indicates
that
a
diskette
drive
is
installed.
Low-
and
High-Base
Memory
Bytes
(Hex
015
and
016):
These
bytes
define
the
amount
of
memory
below
the
640KB
address
space.
The
value
from
these
bytes
represents
the
number
of
1KB
blocks
of
base
memory.
For
example,
hex
0280
is
equal
to
640KB.
The
low
byte
is
hex
015;
the
high
byte
is
hex
016.
Low-
and
High-Expansion
Memory
Bytes
(Hex
017
and
078):
These
bytes
define
the
amount
of
memory
above
the
1MB
address
space.
The
hexadecimal
values
in
these
bytes
represent
the
number
of
1KB
blocks
of
expansion
memory.
For
example,
hex
0800
is
equal
to
2048KB.
The
low
byte
is
hex
017:
the
high
byte
is
hex
018.
Reserved
Bytes
(Hex
019
through
031):
These
bytes
are
reserved.
Configuration
CRC
Bytes
(Hex
032
and
033):
These
bytes
contain
the
cyclic-redundancy-check
(CRC)
data
for
bytes
hex
010
through
hex
031
of
the
64-byte
CMOS
RAM.
The
low
byte
is
hex
033;
the
high
byte
is
hex
032.
|
Reserved
Byte
(Hex
034):
This
byte
is
reserved.
|
Low
and
High
Useable
Memory
Bytes
(Hex
035
and
036):
These
|
bytes
define
the
total
amount
of
useable
memory
above
the
1MB.
|
The
hexadecimal
values
in
these
bytes
represent
the
number
of
1KB
3-20
Model
65
System
Board
—
October
1990

IBM Personal System/2 65 SX Specifications

General

Brand	IBM
Model	Personal System/2 65 SX
Category	Desktop
Language	English