FIC 486-JAL User Manual

486- JAL

MAIN BOARD

USER’S MANUAL

DOC. NO.: 12409
Rev.

Date

:

B

:

MAY

1993

Table of Contents

INTRODUCTION l l l l l l l l l l l l l 1

OVERVIEW

SPECIFICATIONS
MOTHERBOARD LAYOUT
SYSTEM BLOCK DIAGRAM.

........................

.....................

................

...............

INSTALLATION l l l l l l l l l l l l l l 5

CONNECTOR DESCRIPTION
JUMPER DESCRIPTION

INT/EXT BATTERY SELECTION (FOR

CPU TYPE SELECTION
ON-BOARD VGA CONTROLLER

FDD TYPE SELECTION
LOCAL IDE SELECTION
HDD SPEED SELECTION (PDC 20230 ONLY)
CPU SPEED SELECTION (PDC 20230 ONLY)
CPU CLOCK SELECTION

...............

..................

..................

..................

.................

.................

DS12885Q

.............

ONLY) . . 11

........

........

SYSTEM MEMORY l l l l l l l l l l l l 15

MEMORY CONFIGURATION . . . . . . . . . . . . . . . 15

1

1
3
4

5

10

11
11
11
12
12
12
13

Appendix A
AWARDBIOS SETUP l l l l l l l l l l l 17

SYSTEM SETUP CONFIGURATION ............

STATUS PAGE SETUP ..................

OPTIONS PAGE SETUP ..................

SAVE AND EXIT .....................

Appendix B
AMIBIOSSETUP

SYSTEM SETUP CONFIGURATION ............

STANDARD

ADVANCED CMOS SETUP ................

WRITE TO CMOSANDEXIT ...............

CMOSSETUP

.................

. . . . . . . . .

l

a

l l 19

Appendix C
TECHNICALINFORMATION l

SYSTEM I/O ADDRESSMAP
HARDWARE INTERRUPT REQUESTS
DMA ASSIGNMENTS
MEMORY MAP

......................

................

..........

...................

o o

l o l

e

23

17
18
18
18

19
20
21
22

23
25
26
27

N ii-

486JAL

m.................

. . . . . . . . . . . . . . . . .

.

..I . . . . . . . . . . . . . . . . ‘ . . . . . . . . . . . . . . . . ..I.. . ..I... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..I..... . . . . ..I......... . . . . . . . . . . . . ..I..........

INTRODUCTION

OVERVIEW

The

486.JAL

The 486-JAL is a high-performance VESA mother board, offering
outstanding features and speed ideal for building advanced personal
computers or workstations. The board utilizes high grade components
as listed below:

SPECIFICATIONS

Features of this board include:

0

Intel
Dual CPU in PQFP and PGA packages.

0

VIA

0

Supports

Provides page mode DRAM operation.

0

Shadow RAM.

0

128KB

0

One

0

CPU clock output frequency selectable by jumpers.

0

Cirrus GD5426 Local Bus VGA controller.

0

Promise PCD20230 Local Bus IDE controller (optional).

0

Real time clock/calendar.

0

Built-m IDE

l

Two serial ports and one parallel port.

0

PS/2 mouse and PS/2 keyboard connector.

0

Local Bus VGA with 512K/lMB

0

LPM-size board ( 13.0” x 7.8”)

Motherboard

80486DX/80486DX2/80486SX/80487SX

VT82C470

PC/AT chipset.

1MB

up to 32MB of DRAM memory;

BIOS.

16-bit, 120-pin

ISA expansion slot.

HDD/FDD

and Local Bus IDE interface.

/2MB

Video RAM on board.

microprocessor.

-

l-

486JA L

INTRODUCTION

MOTHERBOARD LAYOUT

BANK

1

JCl

JC2

El

n

JC3

a

LL

--Id

N-

j

FDD

HDD

l--J

J45

B

p---l

0

8

E

0

j

-

J24
J17
J16
J18

KEYLOCK SPKR

486JAL

A4otherboard

RESET

Layout

- 2-

486JA L

SYSTEM BLOCK DIAGRAM

INTRODUCTION

CPU

PDC

_lGD5426J=

System Block Diagram

MEMORY
ADDRESS

BUS

MA

,I,

SWEM

ADDRESS

!$
3

iz
g

,

serialport

parallel p

85

7

art

INSTALLATION

CONNECTOR DESCRIPTION

Connector

CNl-

PS/2 Keyboard

CN2

-

PSI2

Mouse

CN3

-

Serial port 1

CN4

-

Serial port2

Pin out

1

2
3
4

5

6

1

2

.

3
4

5

6

1
2
3
4

5

6
7
8

9

1
2
3

4

5

6

7
8
9

Signal Name

Keyboard data
NC
GND

vcc
Keyboard clock
NC

Mouse data

NC

GND

vcc
Mouse clock

GND

Data carrier detect

Receive data

Transmit data

Data transmit ready

GND

Ready to receive data

Request to send data

Clear to send

Ring indicator

Data carrier detect

Receive data

Transmit data

Data transmit ready

GND

Ready to receive data

Request to send data

Clear to send

Ring indicator

- 5-

486JA L

INSTALLATION

Connector

-

CN5

-

Parallel port

CN6

-

VGA connector

CN7

-

Power connector

Pin out

~-

1
2
3
4
5
6
7
8
9

10

11

12

13

14

15

16

17

18-25

-_____

1

2
3
4
5-8
9

10
11-12
13
14
15

-~

1

2

-3

4

5-8

9

10-12

_______

Signal Name

LPT strobe
LPT DO

LPTDl

LPT D2
LPT D3
LPT

104

LPT

D5

LPT D6
LPT D7
LPT acknowledge
LPT busy
Paper end

Selected status
Auto line feed
LPT error
Initiate printer

Select printer

GND
Red

Green
Blue
NC

GND
NC

GND
NC
Horizontal sync

Vertical sync
NC

-­Power good

+

sv

+ 12v

-12v

GND

-5v
+ 5v

______--

______-____---

__p

=

-______

INSTALLATION

Connector

513 -

85

14A

connector

Pin out Signal Name

-

1

2

3

4

5

6
7

8

9

10
11
12
13
14

15

16
17
18

19
20
21
22
23
24

25

26

VP0

GND

VP1

GND

VP2
GND
VP3

Enable video data

VP4

Enable sync signal

VP5

Enable video dot clock

VP6

NC

VP7
GND
Video dot clock
GND

Banking

GND

Horizontal sync

GND
Vertical sync

NC

GND

NC

INSTALLATION

Connector

FDD

-

FDD connector

-

Pin out

2
4
6
8

10
12
14
16
18

20

22
24
26
28
30

3q
3i

1,3,5,7,

9,

11,

15,

17,

19,21,

23,25,

27,29,

31,33

-

Signal Name

Density selection
NC
NC

Index detection
Select motor A
Select drive B
Select drive A
Select motor B
Direction control

Step pulse

Write data

Write enable

Track

Write protect
Read data
Head select
Disk change

GND

13,

0

-

a-

486-JA

L

INSTALLATION

Connector

HDD

-

IDE connector

Pin out

1
2
3
4

5
6
7

8

9

10
11
12
13
14
15
16
17
18
19

20-2

1

22

23

24

25

26

27

28

29

30

31

32

33

34

;b5

36

37

38

39

40

Signal Name

Reset hard disk
GND
HD D7
HD D8
HD D6
HD D9
HD D5

HDDlO

HD D4

HDDll

HD D3
HD D12
HD D2
HD D13

HDDl

HD D14
HD DO
HD D 15

GND

NC

GND

HD I/O write

GND

HD I/O read

GND
IOCHRDY
HD address latch
NC

GND

IRQ 14

IOCSIG

HD Al

NC

HD A0
HD A2
HD chip select 0

HD chip select 1
HD active

GND

-

9-

486JA

L

INSTALLATION

Connector

523

Keylock

Power LED

522

Speaker
connector

521

Reset switch

Jl9

Turbo switch

520

Turbo LED

545

HDD LED

J9

Ext Battery
Connector

&

Pin out

1
2
3
4

5

1
2

3

4

1
2

1
2

1
2

1
2

1
2

3

4

JUMPER DESCRIPTION

Signal Name
Power LED

Power LED
GND

Keylock

GND
Speaker signal

NC
GND
vcc

GND
Reset signal

GND
Turbo signal

LED
Pull high

LED

VCC

Anode +
NC
NC
Cathode

-

Jumper

54

JS

57

525

Function

Display type Mono/EGA/ Color

CMOS DATA Clear Normal Clear
(FOR

DS1287A

Password Reset Normal Reset
(For AWARD BIOS only)

Password Reset Normal
(For AM1 BIOS only)

only)

-

lo-

486JAL

Open

VGA

(default)

Close

,

Reset

.._.._..l..m.._.....m..

_

.._.._.._.._.. _ .._.. -..-..- . . . . .

_..-..1..1..-..1..1..-..-..-..-..-..-..-..-..-..-..-..-

..I.. _..1.._..1.._..-..1..B..m..s*.w..m

SYSTEM MEMORY

~_~~“_“_~~“_~_1_1_“_1-1-1-1

MEMORY CONFIGURATION .

NOTE 1

_“_1~1~__“_“~“_“~“_“~~~~~~~~~~~~~”~”~”~~~~~”~~~“~“~~~~~“~~~”~~~~~~~~~~~~~~~~~“~~~~~~~

:

Bank 0 and Bank 1 are 72-pin SIMM-type sockets.

..I.. _ ..I.. _..w..__

Total Memory Bank

1M

2M
4M

SM
8M

0

Bank

1M

1M 1M

4M
4M

1M

4M 4M

1

16M 16M
17M

20M

32M

16M

16M

16M

1M

4M

16M

NOTE 2 : Bank 0 has the 4MB DRAM on-board and

Bank1 is a 72,pin SIMM type socket.

Total Memory Bank

4M

SM
8M

20M

4M 0

4M lMx1
4M
4M

O#

Bank 1

4Mxl

16Mxl

# On BANK 0, you can install a 72-pin SIMM-type module

(4MxIpcs),or

an SOJ-type DRAM

(IMx4bitx8pcs).

-

1%

486JA L

INT/EXT BATTERY SELECTION

(FOR DS12885Q ONLY)

CPU TYPE SELECTION

INSTALLATION

JC2
JC3
JC4

______

Jll 2-3 shorted l-2 shorted

1

,

2-3 shorted 2-3 shorted

2-3 shorted 2-3 shorted
OFF

OFF

_~~~

’ !:; ;i!;

l-2 shorted l-2 shorted

ON-BOARD VGA CONTROLLER

FDD TYPE SELECTION

- ll­486JAL

;;;;;;

-

INSTALLATION

LOCAL IDE SELECTION

524

Local IDE Enable

l-2

Local IDE Disable
2-3

.

HDD SPEED SELECTION (PDC 20230 ONLY)

516 517

SPEED 0
SPEED 1
SPEED 2 l-2

2-3

l-2

2-3
2-3

l-2

CPU SPEED SELECTION (PDC 20230 ONLY)

CPU SPEED

<=

33 Mhz

>

33 Mhz

518

l-2

2-3

J

- 12­486JAL

CPU CLOCK SELECTION

INSTALLATION

l-2

on
on
on
on
on
on

on
on

off

Off

Off

off
off

Off

off
off

3-4
on
on
on
on

Off

off

Off

off

on

on

on
on

Off

Off

Off

off

5-6 7-8
on on
on

Off on

Off

off off
on on
on
off

off
on

off off

on
on

Off

Off Off

on

Off

on

on on
on

off

Off

Off

on
off

Freq.

mw

24

12
80
40
40
20

66.6

33.3

32

16

66.6
50
50
25

-

CPU Type

486DX-33,

4861)X2-66

486SX-25
486DX2-50

,4861)X-25

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..I.. . . . . . . . . . . ..I.. I...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ..... . .............

SYSTEM MEMORY

“~“~“~“~“~“~“~-~“-“----~----“-“--~---~”-”~”--~”~-~“~-~-~“-”~”-”~-~-~“~“~-~“~“~-~-~“~-~“~-~”~”~-~-~-~-~“~-~“~-~-~

MEMORY CONFIGURATION .

:

NOTE 1

Bank 0 and Bank 1 are 72-pin SIMM-type sockets.

Total Memory Bank 0

1M

2M
4M

5M

8M

16M

17M

20M
32M

NOTE 2 : Bank 0 has the 4MB DRAM on-board and

# On BANK 0, you can install a

(4Mxlpcs),or

Bank1 is a 72-pin SIMM type socket.

Total Memory
4M

SM

8M 4M
20M 4M

an SOJ-type DRAM

1M

1M

4M
4M
4M

16M

16M

16M

16M

Bank 0# Bank 1
4M

4M

(lMx4bitx8pcs).

Bank 1

1M

1M

4M

1M

4M

16M

0

1Mxl

4Mxl

16Mxl

72-pin

SIMM-type module

,

-

1%

486JA L

APPENDIXA

“_“_“.Y_..

. . . .

Y_.._Y_Y_Y_Y

. . . .

_“_..l.._.._..l

e.-YI..-..-Y-Y-..-Y

.-.

. . . . .

_.._Y_Y_.~_Y_...Y-Y_..-..-..-..-..-”-

. . _ . _ . . .” _ . . n . . I .* _ .- ^ Y _ . . _ . . _ -. a .- --

AWARD

.._..I.._.._ . . . . .

*..- ..I.. _..I.._

. . . . .

..s.._..-..-..-..s..s

_

..I..

_.._..I

BIOS

. . . . .

.I.._..I..m..m

_..I.

SETUP

._.._.._..m.._..I

. . . . . . . . . . .

m.._.._..I..I.

. . . . .

I..I.._.._..w..s.._..m..ww

SYSTEM SETUP CONFIGURATION

A SETUP program, built into the system BIOS, is stored in the CMOS
RAM that allows the configuration settings to be changed. This
program is executed when:

User changes system configuration.

(1)

User changes system backup battery.

(2)

System detects a configuration error and asks the user to run

(3)

the SETUP program.

After power-on RAM testing, the message below appears:

“TO ENTER SETUP BEFORE BOOT, PRESS CTRL-ALT-ESC”

Press

appears:

Halt On

I

Cache

Shadow
Security

“CTRL+

ALT+ ESC” to run SETUP. The screen below

ROM ISA BIOS (VIA)

Award Software, Inc.
Base Memory: 640K
Extended Memory : 3072K

:

All Errors

:

Internal Cache

:

System & Video

:

Disabled

Expanded Memory: OK
Other Memory
Total Memory

Boot Sequence: A, C
Virus Warning

NumLock

:

384K

: 4096

:

Disabled

Boot Status : On

Drive

@

Drive

D

Alt-Fl for Menu Help
Page 01 : Status Page

:
:

None (****Mb)
None (****Mb)

PgDn = Options Page

CYL Head Sector
0 0
0 0 0 0 0

- 17­486JA

L

Precomp

0 0 0

FlO exits

F2 change colors

Landzone

AWARD BIOS SETUP

STATUS PAGE SETUP

The SETUP program is completely menu-driven. Use the arrow keys

to select an entry;“+

I-”

keys to change an entry; and “F 10” key to
exit. Help messages are displayed in the window on the screen when
you press “Alt-F

1 Y’

A sample screen of the Status Page SETUP is displayed above.

System BIOS automatically detects memory size, thus no changes are

necessary. After the changes are made, press “FlO” to exit.

OPTIONS PAGE SETUP

Moveing around the Options Page Setup program is similar to

moving around the Status Page Setup.

Cache Control

256K/384K Relocation: Disabled

Cache Timing
Dram Timing
Video Cacheable

System Cacheable

\

Alt-Fl for Menu Help
Page 02 : Options Page F2 change colors

PgUp = Status Page

:

Normal

:

Fast

:

Enabled

:

Enabled

FlO exits

1

+

Users are not encouraged to run the option Status Page SETUP
program unless absolutely necessary and user understands and knows

how to modify the settings. Improper SETUP may cause the system
to fail, so consult

de*aler

before making any changes.

SAVE AND EXIT

When you have made changes under SETUP, press F 10 to exit. If no
changes have been made, press F 1 to exit; otherwise, press FS to save
and exit.

- 18­426J2 E

SYSTEM SETUP CONFIGURATIQN

The SETUP program, built into the system BIOS, is stored in the
CMOS RAM so that the configuration settings can be changed. This
program should be executed when

User changes system configuration”

(1)

User changes system backup battery.

(2)

System detects a configuration error and asks the user to run

(3)

the SETUP program.

After power-on RAM testing, the message below appears

“Press < DEL,> if you want to run SETUP”

Press “DEL” to run SETUP and the screen below appears:

AMIBIOS SETUP PROGRAM -BIOS SETUP UTILITIES

(C) 1992 American Megatrends Inc., All Rights Reserved

STANDARD CMOS SETUP

AUTO CONFIGURATION WITH BIOS DEFAULTS

,4UTO CONFIGURATION WITH POWER-ON

I

Standard CMOS Setup for Changing Time, Date, Hard Disk Type, etc.

ADVANCED CMOS SETUP

CHANGE PASSWORD

AUTO DETECT HARD‘DISK

HARD DISK UTILITY

WRlTE TO CMOS AND EXIT

DO NOT WRITE TO CMOS AND EXIT

:

DEFAlJLTS

ESC : Exit &

-+? Se1 F2/F3

: Color FlO

:

Save & Exit

Use & and ? keys to move cursor to your chosen SETUP utility and
press “Enter” to run the selected program.

_--

-

i9-

486JA L

AM1 BIOS SETUP

STANDARD CMOS SETUP

AMIBIOS SETUP PROGRAM -STANDARD CMOS SETUP

(C) 1992 American Megatrends Inc., All Rights Reserved

Date (mnldatelyear)

Time

(hour/min/sec)

Hard disk C: Type
Hard disk D: Type
Floppy drive A:
Floppy drive B:
Primary display
Keyboard

Fri, Jun 11 1993 Base memory:640 KB

:
:

11:32:03

:

Not Install

:

Not Install

:

1.2MB,

5t/4”

:

Not Installed

:

VGA/PGA/EGA

Installed

:

Cyln Head WPcom

Ext. memory

LZone

6 7 8 9 101112

13 14

15 16 17 1819

20 21

22 23 24 2526

2728 29 30 311 2

Sect Size

:

3072 KB

The SETUP program is completely menu driven; use the arrow keys
to select an entry;
key to exit.

“PgUp”/“PgDn”

keys to change an entry; and

“Esc”

Help messages are displayed in the window on the screen

when “Alt-F 1” is pressed.
The Standard CMOS SETUP screen is shown above. System BIOS

automatically detects memory size, thus no changes are necessary.
After the changes are made,

press”Esc”

to exit.

M 20-

486JA L

ADVANCED CMOS SETUP

AM1 BIOS SETUP PROGRAM -ADVANCED CMOS SETUP

(C) 1992 American Megatrends Inc., All Rights Reserved

Wait For <

Fl> IfAny

efiesh

Sequencd

Error

System Boot Up
External Cache Memory
Internal Cache Memory
Password checking Option
Video ROM Shadow COOO, 32K
Adaptor ROM Shadow

Adaptor ROM Shadow
Adaptor ROM Shadow
Adaptor ROM Shadow

BIOS Cacheable Option

Video Cacheable Option

256K Relocate Option

Decouple R

FAST A20 PORT 92H

CO M 1 Select
COM2 Select

Parallel port address

C800,32K
DOOO,

D800,32K

EOOO,

32K

64K

:

Enabled

:

A:, C:
Enabled
Enabled

:

Setup

:

Enabled

:

Disabled

:

Disabled

:

Disabled

:

Disabled
Enabled
Enabled
Disabled
Disabled
Enabled
Enabled
Enabled

0378H

ID E Select
FDC Select
Local IDE Select

AM1 BIOS SETUP

Enabled
Enable
Disabled

1

ESC: Exit

F5 : Old Values F6 : BIOS Setup Defaults

Se1

(Ctrl)

Pu/Pd

:ModifL

Fl

F7 : Power-on Defaults

:

Help F2/F3

:

Color

Moving around the Advanced CMOS SETUP program works in the
same way as the Standard CMOS SETUP.

Users are not encouraged to run Advanced CMOS SETUP program.

Your system should have been fine-tuned before shipping. Improper

SETUP may cause the system to fail, consult your dealer before

making any changes.

N 21-

486JAL

AM1 BIOS SETUP

WRITE TO CMOS AND EXIT

After making changes under SETUP, press

“Esc”

to return to the

main menu, move cursor to “Write to CMOS and Exit”,

to change the CMOS SETUP.
again and then “y”,

AMIBIOS SETUP PROGRAM - BIOS SETUP UTILITIES

AUTO CONFIGURATION WITH POWER-ON DEFAULTS

ESC : Exit k +?

then the CMOS SETUP will not change.

(C) 1992 American Megatrends Inc., All Rights Reserved

STANDARD CMOS SETUP

AUTO CONFIGURATION WITH BIOS DEFAULTS

ADVANCED CMOS SETUP

CHANGE PASSWORD

Write to CMOS and Exit (Y/N) ? Y

Write the settings to the CMOS and Exit

If no changes are made, press ESC

I

F2/F3 : Color FlO

Sel

:

Save & Exit

and

press “y”

- 22­486JAL

APPENDIXC

TECHNICAL

INFORMATION

SYSTEM I/O ADDRESS MAP

Hex Range Usage

OOO-OlF

020-03F
02E 1

02E2 & 02E3
040-05F Timer 8254.2

060-06F

06E2 & 06E3

070-07F

080-09F

OAO-OBF
OAE2 & OAE3
OCO-ODF
OEE2 & OEE3

OF0

OF 1

OF&OFF

lFO-lF8

DMA controller 1,8237A-5
Interrupt controller
GPIB (Adapter 0)
Data Acquisition (Adapter 0)

8042 (Keyboard)
Data Acquisition (Adapter 1)
Real-time clock, NMI (non-maskable interrupt) mask
DMA page registers,
Interrupt controller 2,8259A
Data Acquisition (Adapter 2)
DMA controller 2,8237A-5
Data Acquisition (Adapter 3)
Clear Math Coprocessor Busy
Reset Math Coprocessor
Math Coprocessor
Fixed Disk

1,8259A,

74LS612

Master

M 23­486JAL.

--

TECHNICAL INFORMATION

Hex Range

300-3

1F
360-36F
37%37F
380-38F

390-393

3AO-3AF
3BO-3BF
3CO-3CF
3DO-3DF
3FO-3F7

3F 8-3FF
42E 1
62E 1
790-793
82E 1

A2El
B90-B93

C2El

E2El

1390-1393

2390-2393

Note: I/O address, hex 000 to OFF, are reserved for the m other board
I/O. Hex 100 to 3FF are available on the I/O channel. The base

addresses for GPIB and Data Acquisition are shown.

Usage

-

Prototype card
PC network
Parallel printer port 1

SDLC, bisynchronous 2
Cluster
Bisynchronous 1
Monochrome display and printer adapter
Enhanced graphics adapter

Color/graphics monitor adapter
Diskette controller

Serial port 1

GPIB (Adapter 2)

GPIB (Adapter 3)

Cluster (Adapter 1)

GPIB (Adapter 4)

GPIB (Adapter 5)

Cluster (Adapter 2)

GPIB (Adapter 6)

GPIB (Adapter 7)

Cluster (Adapter 3)

Cluster (Adapter 4)

- 24­486JAL

TECHNICAL INFORMATION

HARDWARE INTERRUPT REQUESTS

IRONo.

IRQO

IRQ3 Serial port 2

IRQ 13
IRQ 14
IRQ 15

IRQl

IRQ4

IRQS

IRQ6
IRQ7
IRQ8

IRQ9

IRQ 10

IRQll

IRQ 12

jFundion

Timer output

Keyboard

Serial port 1
Available
FDD controller
Parallel port 1
Real-time clock
Available
Available
Available

PS/2 compatible mouse

Math coprocessor

HDD controller

Available

H 25

486JA L

TECHNICAL INFORMATION

DMA ASSIGNMENTS

I

Ikvel

t-

DMAO
DMA 1

DMA2
DMA3

DMAS

DMA6

DMA7

Assigned devices
Reserved
Reserved
Floppy controller (g-bit)

Reserved

Reserved
Reserved
Reserved

N 26­486JAL

MEMORY MAP

TECHNICAL INFORMATION

IFFFFFFH

OlOOOOOH

OOFFFFFH

OOFOOOOH

OOEFFFFH

00C8000H

OOC7FFFH

OOCOOOOH

OOC8FFFH

OOAOOOOH

OOSFFFFH

OOOOOOOH

Maximum

Addressable

Extended RAM

STSTEM BIOS

ROM

ROM ON I/O

ADAPTER

VGA BIOS ROM

GRAPHICS

SYSTEM MEMORY

DISPWY

BUFFER

32MB

IMB

640K

- 27­486JA L