AST RESEARCH MegaPlus II User manual
TM
User's
Manual
Af
.1
RESEARCH
INC.
MegaPlus
II
Memory
Expansion and 1/0 Card
for
the
IBM Personal Computer,
IBM
PC·XT, and
Other PC·Compatible Systems
User's Manual
August, 1983
AST
RESEARCH, INC.
Irvine, California
(714)
540-1333
FIRST
EDITION (August. 1983)
IBM is a registered trademark
of
International Business Machines Corporatio
n.
Compaq
is
a trademark
of
Compaq Computers. Inc.
MegaPlus
II
. MegaPak. SuperPak. SuperDrive. and SuperSpool are trademarks
of
AST
Research. Inc.
Copyright © 1983 AST Research. Inc. All rights are reserved. including those to
reproduce this book
or
parts thereof
in
any form without permission
in
writing from
AST
Res
ear
ch. Inc.
TABLE
OF
CONTEl\'TS
SECTIO]'o;
1. Il\TRODUCI:\,G
THE
MEGAPLlJS
11
. I-I
1.1
Compatibility.
.
..
. . . . 1
-3
1.2 Non-PC-DOS Operation .
1-4
1.
3 MegaPlus
II
Board
Layout.
. . . . . . . . . . . . . . . . . . . . . . . .
..
1-4
I A This Manual
1-4
IA.I
Syntax Conventions
.....
.
.....
1-6
SECTIO]'o;
2.
MEGAPLUS
II
MEMORY
CONFIGURATIOl\ . . . . . . . . . . . . . . . . 2-1
2.I Removing the PC System Unit
Cover.
. . . . . . . . .
2-1
2.2 MegaPlus
II
Memory Switch Settings. . . 2-2
2.2.1 MegaPlus
1I
Starting Memory
Addres,
...
..
. . 2-3
2.2.2 Parity Check Enable
............
.
...
. . . .
....
.
..
2-4
2.3 PC System Board Switch
Configuration.
. . . 2-5
2.3.1 PC-I System Board Switch Settings
...
..
....
. .
...
2-5
2.3.2 PC-2 System Board Switch
Settings.
2-6
2.3.3
PC-XT
System Board Switch
Settings..
.
...
2-7
2A
Installing Multiple Memory Boards . . . . . . . . . . . . . . . . . 2-8
2.4.1 Installing a Board
"Below"
the MegaPlus
1I
..
...
. 2-8
2.4
.2 Installing a Board
"Above"
the MegaPlus
II
2-9
2.5 Installing Additional Memory on the MegaPlus
II
...
..
...
2-9
2.6
Troubleshooting Memory Problems
.....
. . .
.. ..
.....
2-10
SECTION
3.
SERIAL
ASYNCHRO~OUS
COMMUNICATION . .
..
...................
3-1
3.1 Setting Up Serial Port
#1
............
.
..
. .
.....
....
. . 3-2
3.2
If
Your System Already Has a Serial Port . .
....
.
..
..
...
3-2
3.3 RS-232 Connector Pin List for Serial Port
#1
... ...
.
....
3-3
3.4
Disabling Serial Port
#1
. . .
......
.
...................
3-5
3.5 Option
S:
Serial Port #2
............
.
......
.. ..
....
..
3-5
3.6
Verifying Your Serial #2 Configuration
..
.
.............
3-5
3.7
DTE
and
DCE
Interface Selection for Serial #2
.........
3-6
3.8 Setting
Up
Serial #2 for
DCE
Configuration
....
.
..
.
..
..
3-6
3.9
DCE
Configuration: Serial #2 RS-232 Pin
Connector Listing
......
..
.......
.
.........
.
...
.
.. ..
3-7
3.10 Installing the Serial #2 Interface Cable
..
...
. .
..
.
... ...
. 3-7
3.11
Programmin
g the Serial Port
............
.
..
....
.
..
...
3-9
3.12 Disabling Serial Port #2
...........
.
......
..
..
.
...
. . 3-10
iii
TABLE OF CONTENTS
(Continued)
SECTION
4.
PARALLEL
PRINTER
PORT
(OPTION
P)
............
.........
..
.. ..
...
.4-1
4.1
In
stalling the Inte
rf
ace Cable ...
.........
.
...........
..
4-1
4.2 Reconfiguring Your Parallel Port for
Multiport Systems
...........
...
..
..
...
.
...
.
...
.4-2
4.3
Programming
the Parallel Port
..
..
....
..
..
.
....
. . .
....
4-3
4.4
Printer Port Connections .
..
.
...
.
.....
..
.
...
......
..
.
.4-3
4.5
Disabling the Parallel Printer Port
.....
.
..........
.
...
.4-5
SECTION
5.
CLOCK-CALENDAR
FEATURE
..
.
.........
5-1
5.1
The
Cl
ock-Calendar
Battery . .
...............
..
.......
5-1
5.2
Preparing
Your
Working DOS Diskettes . .
.....
..
.....
. .5-2
5.3 The
SETCLOCK
Utility: Setting the MegaPlus
II
Time
and Date
.......
.
......
..
..............
.
...
..
.5-3
5.4
Device Addressing
of
the Clock-Calendar .....
...
.
...
..
.5-4
5.5
Disabling the Clock-Calendar on Your MegaPlus
II
....
...
5-4
SECTI
ON 6.
MEGAPAK
...
..
...........................
6-1
SECTION
7.
GAME
ADAPTER
PORT
.....
..............
7-1
7.1
In
stalling the
Game
Adapter
Pi
ggyback Board
....
..
...
. .7-1
7.2
Device Addressing
of
the
Game
Adapter
.....
....
.
...
..
.7-1
7.3 Disabling the
Game
Adapter Port .
...
.
...
.....
..
..
.
....
7-2
SEC
TIO:"ol
8. I
NS
TALLING YOUR MEGAPLUS II BOARD
..
8-1
8. 1 Testing the New Installation .
..
...
..
..........
.
.......
8-2
SEC
TIO
N 9.
liSE
R UPGRADE
L~FORMA
TION
......
. . .
..
9-1
APPENDICES
APPENDIX
A:
RECOMMENDED
SERIAL
PORT
CA
BLING
.............
.
.................
A-I
APPENDIX
B:
SWITCHING
BETWEEN
LPT1 AND LPT2
...
B-1
APPENDIX
C:
CLOCK-CALEN
DAR
CHIP
......
...
.
..
.
....
C-I
APPENDIX
0:
PATCH
PROCEDURES
........
....
........
0
-1
APPENDIX
E:
WIRlNG
RS
-232
SERlAL
INTERFACES
.....
E- I
iv
TABLE OF CONTENTS
(Continued)
FIGURES
Figur
e
1-1
.
MegaPlu~
II Board Layout . . . . .
1-5
Figur
e 2-
1.
Removing
System Unit
Cover
. . . . . . ". .
.. ..
2-2
Figure
2-2.
Starting
Addres
s Settings
.2
-3
Figure
2-3. Parity
Check
Enable Setting . .2-4
Figure
2-4.
PC-l
System Board Switch Settings ...
..
. "" . .
...
.2-5
Figure
2-5.
PC-2
System B
oard
Switch
Settings .2-6
Figure
2-6
.
PC-XT
System Board Switch Settings .
..
"......
2-7
Figure
7-1 .
Game
Adapter
Piggyback B
oard
Layout
..
.
....
7-2
Figure
E-l.
The
Ideal:
Terminal
to
Modem
. . . . . . . . . . .E-3
Figure
E-2.
Example
of
a Specific
DTE
to
DTE
Interf
ace
..
....
E-4
Figure
E-3.
AST
R
esearch
Board"s Serial
Port
DTE
to
NEC
7700 Series Serial
DTE
Printer.
.E-6
Figure
EA.
Serial Interface
Form
Schematic
Diagram
s . .
...
E-7
..
"""
.....
Back
of
Manual
v
(This page intentionally left blank)
vi
SECTION 1
INTRODUCING THE MEGAPLUS
II
The
AST
Research
MegaPlus
IpM board is a versatile and powerful
memory
expansion and data 110 accessory for
your
IBM
Per,on
al
Computer
(PC) family.
The
generous
range
of
the expansion
memory
size. the real time Clock with battery backup. and the
RS-232 asynchronous Serial communications port (all standard).
along with the optional Second Serial port, Parallel
printer
port. and
Game
adapter port make the
MegaPlus
II
board the ultimate
in
expansion
hardware
.
Depending
on the options selected, the
MegaPlus
II
board
supplie,
up
to 512KB (kilobytes)
of
additional Random Access
Memor
y
(RAM).
With this larger storage capacity you can run any
PC-compatible
applications software requiring additional memory
and expand the capacity
of
some
of
your
existing
programs
, such as
spreadsheet models.
As a bonus.
AST
Research gives you two valuable utility programs:
SuperDrive
TM,
a disk emulation
program
allowing you to use part
of
your
memory
as a superfast "electronic disk
drive"
; and
SuperSpoolTM, an intelligent print
spooler
allowing you to output
files to a
printer
without tying up
your
PC
.
These
utilities are
discussed
in
the SuperPak User's Manual.
Your
MegaPlus
II
board
is
available with
64.
128. 192,
256.
384.
or
512 kilobytes
of
RAM
memory.
If
you
prefer.
you can start
off
small and install
AST
Research
memory
upgrade kits and the
MegaPak
piggyback
board
as you need
more
memory
space.
Standard features
• A real-time
Clock-Calendar
with battery backup so that
you
don't
have to
enter
the time and date
every
time you
start
your
system.
The
battery
power
is only used when
your
system is turned off.
1-1
• An RS-232C Serial interface to be used with a modem,
serial printer. remote display terminal, other serial device,
or
as an asynchronous communications port to another
computer
or
peripheral operating under separate
asynchronous
commu
nications software control. (Note: a
current loop teletype interface
is
not supported.)
• Up to 256K
of
RAM memory, available in
64K
increments.
•
The
SuperPakI'M utility diskette containing SuperDriveT
M,
SuperSpoolTM. clock software, and the
RAMCLEAR
memory initialization utility program.
NOTE
For information on the SuperPak utilities, see
your SuperPak User's Manual.
Available options
• A Parallel printer port to be used for connecting a parallel
printer to the
Pc.
• A Second
RS
-232C Serial port (serial #2, configurable as
DTE or
DCE
).
•
The
MegaPak
TM,
providing 128K
or
256K
of
additional
memory. which brings the MegaPlus
II
board total to
384K or 512K bytes,
• A Game
adapter
port which can be used with an IBM-
compa
tible joystick.
These options may be purchased
onboard,
or installed by the user at
a later date. (Upgrade kits are available from
your
dealer.)
1-2
1.1 Compatibility
The
McgaPlus
II
is
completely compatible with all existing. 18i\1 PC
types.
It
is
also compatible with the
Compaq
and
other
IBM
looJ.;
-
alikes.
The
three existing IBM PC
modeb
are defined
in
thi,
manual as follows:
I.
Th
e PC-1
is
the original IBM Personal
Computer
The
system board contains 64K
of
memor)
.
The
sy,
t
cm',
maximum
mcmory
capacity
is
640K. System hoa
rd
switches, howe
ver
, recognize a
maximum
of
5441<..
2. The PC-2
is
the newer, updated version
of
the PC- I. The
system board
mu
st be fully populated with
2561<.
of
memor
y before utilizing any expansion board memory .
If
your
PC
-2 is
not
fully populated, then the AST Research
Memory
Upgrade
Kit
(P
IN MP-()()9)
can
be used for this
purpose
.
The
maximum
memory
capacity
of
this system
is
640K.
3.
The
PC-XT
comes
standard with 128K
of
memory
. The
system board is expandable
to
256K. Unlike the PC-2, the
system
board
does not have to be fully populated before
using expansion
board
memory
; you may,
however,
use
the
AST
Research
Memory
Upgrade
Kit
(P
IN MP-()()9)
on
your
system
board,
if
desired. The
XT
computer
automatically recognizes
memory
up to a
maximum
of
640K.
The
XT
comes
with a standard serial
port
configured
as
COM
I.
Your
MegaPlus
II
board
comes
with a standard
serial port that should
be
reconfigured as
COM2
to avoid
addressing conflicts with
COM
I. Section 3
of
this manual
contains the necessary reconfiguration instructions.
1-3
1.2 Non-PC-DOS Operation
All references to operating system commands
in
this manual assume
operation under PC-DOS. The MegaPlus II board
's
hardware is
completely IBM-compatible and will function properly under other
IBM-approved operating system software.
Of
course, configuring
the I/O ports under another operating system requires the use
of
commands
specitic to that operating system. See your operating
system manual for the appropriate
co
mmand syntax.
1.3 MegaPlus
II
Board Layout
Figure
I-I shows the MegaPlus II board layout with major features
labeled.
1.4 This Manual
If you are familiar with the memory and I/O capabilities that the
MegaPlus
II
board provides, and you have a 64K
PC-l
system with
no current I/O options (other than the printer port
on
an IBM
Monochrome Adapter), all you have to do
is
to set the PC system
switches for the amount
of
memory
your
system will have with
your MegaPlus
II
board installed and
you're
set to go. However,
we strongly recommend that you thumb through this manual at your
leisure, and read up on the SuperPak software utilities.
If you have other I/O capability
in
your
present system, you may
want to scan the approp
ri
ate chapters
of
this manual. This might
save you some headaches later on.
If
you have problems, you
should certainly go back and read the appropriate chapter for some
helpful hints, and to clarify the condi
ti
ons necessary for your
memor
y and/
or
I/O option
to
function properly.
1-4
NOTE
BE
SURE
TO
FILL OUT
YOUR
WARRAt'lTY
CARD AND
MAIL
IT
IN.
....
I
til
""l
~.
c:
..,
~
7'
....
~
~
(JQ
~
....,
::
'"
=:
C;j
o
~
..,
Q.
t'"'
~
'<
o
c:
....
Screw
Set
Assembly<
J5·MegaPak
Connector
(Optional)
Screw
Set
Assembly<
Asynchronous
Serial
Port
#2
Connector
(Optional)
J4·DCE
Configuration
J3·DTE
Configuration
DTE/DCE
Selection
Jumper
Block
J2·Paraliel
Printer
Port
Connector
(Optional)
..
""
::
'!'''
:::
"'\-.0
1\' '"
.,
Y I I I ; ;
•••
;;;
•••
:=
I I I I M
II
nM
Bank
1
(64K;
Bank
2
(128K)
Bank
3
(192K)
0,
01
1 104
""
00
C~l
101
.,£-'\
LJ
.
"~
I
""
Bank
4
_~
,
LJ
LJ"
'"'
"
rot
:J
00
,
...
,
(
256K~I~
j
JJJJJJJJJJdJJJ
JJ
JJtt'
JI
~
U u
ASIt
~
~
" [
1~::r.::::
021
1
04
001
"
201
1
.0
-,
Screw
Set
Assembly
"
M
Screw
Set
Assembly<
To
locate
pin
#1
of
an
integrated
ci
rcuit
(IC)
find
the
notch
on
the
chip
assembly.
Screw
Set
Assembly<
S1-Swltch
#1
Game
Adapter
Piggyback
Board
Interface
Connector
Notch--,
Pin
#1-
f1
o Parallel
Port
Output
Selection
Jumper
Block
*
For
Se
curing
Opt
ional
MegaPak
Board
...
For Securing Optional
Game
Adapter Piggyback Board
I
,
IRQ
Enable
Jumper
Block
Serial
Port
Output
and
Clock
Selection
Jumper
Block
Asynchronous
Serial
Port
#1
Interface
Connector
1.4.1 Syntax Conventions
The
following conventions
are
used in this manual to present
comma
nd statement formats:
1-6
I. A syntax element written in uppercase letters
or
special
symbols
other
than
brackets
, braces,
or
ellipses is a
keyword
and must be entered exactly as shown.
Keywords
can be entered in any combination
of
upper-
and l
owe
rcase letters.
2.
Square
brackets
([ ]) indicate an optional
term
which
is
includ
ed
or omitted at the
user
's
discretion.
The
brackets
are
not part
of
the input.
3. Lowercase letters represe
nt
user-defined parameters.
These
p
arameters
must sa
ti
sfy the conditions specified in
the
co
mm
and description.
4. Pressing
th
e
Enter
key
is
not necessary unless explicitly
stated in this manual (usually with the notation
..
<e
nter >
").
) SECTION 2
MEGA
PLUS II
MEMORY CONFIGURATION
In order to use the memory on your MegaPlus
II
board. you must
properly configure both the MegaPlus
II
board and the PC
sy~tem
board. Section 2.2 covers configuration
of
the switches on the
MegaPlus
II
board. Section 2.3 describes configuration
of
the PC
system board switches. The system board configuration process
varies, depending on whether you have a PC-I , PC-2,
or
PC-XT.
Section 2.4 covers the installation
of
other memory expansion
boards
in
your PC along with the MegaPlus
II
.
2.1 Removing the PC System Unit Cover
It
takes only a few minutes to remove the cover from the PC and
install the MegaPlus
II
board into one
of
the empty slots
in
your
PC's
system board. This manual has all
of
the necessary
instructions. Instructions for removing the cover and setting the
switches on your system board are also contained
in
your IBM
Personal
CompUTer
Guide to Operations.
CAUTION
Be
sure that the power switch
is
otT
and the
A.C. cord
is
removed from the system unit.
Turn
oft:
any other equipment connected to
the computer. Installing any component while
the power
is
on can permanently damage
your computer and its components.
STEP
1. Looking at the system unit from the rear, find the
mounting screws
in
the back panel. (There are two screws, found
in
the lower corners, in the PC-I. There are four, one
in
each corner,
in
the PC-2 and PC-XT.) Remove the screws, using a flathead
screwdriver
or
a hex wrench.
2-1
Figure 2-1. Removing System Unit Cover
STEP
2. Slide the system unit cover towards the front. When the
cover will go
no
further, carefully tilt
it
upwards and remove
it
from the system. See Figure 2-1.
2.2 MegaPlus II Memory Switch Settings
Switch
#1
(refer
to
Figure I-I) on the MegaPlus
II
board controls
two different functions related
to
the memory on the board. The
two functions which must
be
configured are:
I.
The starting address
of
the MegaPlus
II
board
2. Parity checking (enabled or disabled)
These functions are controlled
by
setting various positions
of
Switch
#
I.
The following two sections describe these switch sett
in
gs
for the
MegaPlus II board.
2-2
2.2.1 MegaPlus
II
Starting Memory Address
The MegaPlus
II
board must be properly configured to indicate the
amount
of
memory installed below
it
or,
in
other words, what its
starting address should be. Positions 1 through 4
of
Switch
#1
are
used
to
set the MegaPlus
II
board's starting address. Figure 2-2
shows the MegaPlus
II
's starting address settings.
Depending on the type
of
PC that you have, you will use one
of
the
following three settings for the MegaPlus
II
board's starting address.
PC-I:
When installing the MegaPlus
II
board
in
a
PC-I,
configure
the MegaPlus II's starting add
re
ss
to the 64K setting
in
Figure 2-2.
PC-2: When installing the MegaPlus II board
in
a PC-2, a Compaq,
or other compatible system with a 256K system board, configure the
MegaPlus II's start
in
g address to the 256K setting
in
Figure 2-2.
MegaPlus II Starting Memory Address
Maximum
Usable RAM
Starting
Address
S1
S2
S3
S4
On
MegaPlus
II
64K(:10000)
ON ON ON OFF
512K
128K
(:20000) ON ON OFF ON
512K
192K
(:30000) ON ON OFF OFF
448K
256K (:40000)
ON
OFF ON ON
384K
320K
(:50000) ON OFF ON OFF
320K
384K
(:60000) ON OFF OFF ON
256K
448K
(:70000) ON OFF OFF OFF
192K
512K (:80000) OFF ON ON ON
128K
576K
(:90000)
,OFF
ON ON OF':.,!
64K
IiIIIiI
On
~
12345678
..
(j)
00000000
MegaPlu8
II
Switch
#1
Figure 2-2. Starting Address Settings
2-3
PC-XT:
When
installing the MegaPlus
II
board in a
PC-XT,
configure
the
MegaPlus
II's
starting address to the sett
in
g
in
Figure
2-2 which
corresponds
to the amount
of
memory
installed on
the
PC-XT
system
board.
Notice
that the
MegaPlus
II automatically begins limiting the
amount
of
usable
memory
on the board when its starting address
is
configured
at 192K
or
higher.
The
MegaPlus II board can be
addressed only within the first 640K
of
the
PC
, and its starting
address
can be no higher than 576K. This
is
to prevent conflicts
between memory on the MegaPlus
II
and areas reserved for the
monochrome
and
color
display boards.
2.2.2 Parity Check Enable
Position 7
of
Switch
#1
on your MegaPlus
IJ
board can be set to
enable
full parity
error
checking. In
order
to
ensure
the highest
possible data integrity,
it
is
recommended that the parity check
function
of
the board always be enabled by leaving this switch ON.
If,
how
ever,
you have a particular application
in
which you wish
to
disable parity checking, then you can do so by turning position 7
OFF.
See
Figure
2-3 for the location
of
this position.
2-4
On
.-
.(f)
Parity
Check
Enable
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DDDDDDDD
MegaPlus II
Switch #1
8-7
ON = Parity Enabled
8-7
OFF
=Parity
Disabled
Figure 2-3.
Parity
Check Enable Setting
2.3 PC System Board Switch Configuration
The PC-l and PC-2 must be told the exact amount
of
total memory
installed
in
the system. This
is
done
by
configuring switches on the
system board. The switch settings for these two PC models are
described below
in
Sections 2.3.1 and 2.3.2. The PC-XT
is
slightly
different; its switch settings are described
in
Section 2.3.3. You
may also want
to
refer
to
the appropriate IBM Guide to Operations
manual for your particular PC model.
2.3.1
PC-l
System Board Switch Settings
Figure 2-4 should be used if you are installing your MegaPlus
II
board
in
a PC-I. To determine the correct system board switch
setting, add together the amount
of
memory on the system board
(64K) and the amount
of
memory on the MegaPlus II. Set the PC-l
system board Switch
#2
to
the corresponding total from Figure 2-4.
Total
Memory
Installed
in
PC·1
Total
Memor~
S1
S2 S3
S4
64K
ON ON ON ON
128K
ON OFF ON ON
192K
ON ON OFF ON
256K
ON OFF OFF ON
320K
ON ON ON OFF
384K
ON OFF ON OFF
448K
ON ON OFF OFF
512K
ON OFF OFF OFF
544K
OFF OFF OFF OFF
\...
..,.
/
On 1 2 3 4 5 6 7 8
..
[JtJDODDDD
PC·1
System Board
Switch
#2
Figure 2-4.
PC-l
System Board Switch Settings
2-5
Notice that the system board switches for the
PC-l
have a
maximum setting
of
S44K, even though you may
in
sta
ll
up to 640K
in
the computer. Many
"ca
nn
ed"
application programs available for
the
PC
get "confused" when the switches are set for S44K; we
recommend that if you have more than
SI2K
in
stalled
in
your
PC-I
, that you use a setting
of
SI2K.
The excess beyond that
sett
in
g is still usable by SuperDrive a
nd
SuperSpool, as well as
cer
tain other programs.
If
your
PC-l
is equipped with
th
e IBM Expansion Unit and has the
n
ew
ROM BIOS installed, then you can address a full 640K, and
you should use the switch sett
in
gs for the PC-2 (see Figure 2-S).
2.3.2 PC-2 System Board Switch Settings
Figure 2-S should be used if you are installing your MegaPlus II
board
in
a PC-2.
To
determine the correct system board switch
setting, add togeth
er
the amount
of
memory on the system board
Total
Memory
Installed
in PC-2
Total
Memor;t
S1
S2
S3
S4
S5
64K
ON
ON
ON
ON
ON
128K
ON
OFF
ON
ON ON
192K
ON
ON
OFF
ON ON
256K
ON
OFF
OFF
ON
ON
320K
ON ON
ON
OFF
ON
384K
ON
OFF
ON
OFF
ON
448K
ON ON
OFF
OFF
ON
512K
ON
OFF
OFF
OFF
ON
576K
ON
ON
ON
ON
OFF
640K
ON
OFF
ON
ON
OFF
'-.
~
/
On
2
345
678
6-
00000000
PC-2
System
Board
Switch
#2
Figure 2-5. PC-2 System Board Switch Settings
2-6
and the amount
of
memory on the MegaPlus II. Use the appropriate
total from Figure 2-5. Please note that when you include memory
on the MegaPlus
II
in this total, that your system board must be
fully populated with 256K.
If
your PC-2 system board does not
contain 256K, do not include the MegaPlus II memory in the total
system memory. Please refer to Section 1.1
of
this manual for
further clarification on this.
2.3.3 PC-XT System Board Switch Settings
The
PC-XT differs from the PC-1 and PC-2
in
how its system
board switches are configured. In the PC-XT, the system board
switch tells the computer only the amount
of
memory installed on
the system board, and does not include any memory which may be
installed on an expansion board such as the MegaPlus II. The PC-
XT
will automatically recognize the expansion board memory, and
will include this memory in the total system memory, up to a
maximum
of
640K. Furthermore, it is not required that you fully
populate the PC-XT system board before you can use the memory
on an expansion board. Using Figure 2-6, configure the system
board switches for the amount
of
memory on the
XT
system board
(l28K
in
a stock PC-XT).
Memory
On PC-XT System
Board
System
Board
Memory
128K
192K
256K
On
..
S3
S4
OFF ON
ON OFF
\""
OFF ¥
OF~
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DDDOODDD
PC-XT
System
Board
Switch
Figure 2-6.
PC-XT
System Board Switch Settings
2-7
