Acer 486 User manual

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System Board
System Board 1-1
This high-performance, 32-bit personal computer system is based on
the 486 series microprocessor. It features the single-chip upgrade
technology which allows maximum ease and flexibility for upgrading
the system. It is fully compatible with the IBM PC/AT and is suitable
for use as a Windows workstation, CAD/CAE/CAM workstation, UNIX
personal workstation or desktop PC.
The system board accommodates an ISA riser card slot and two 72-
pin SIMM sockets that can hold a maximum memory of 36 MB. The
system architecture is based on the VESA local bus featuring an
onboard VGA. The VGA memory is expandable to 1 MB or 2 MB.
In a LAN environment, the system supports 16-bit Arcnet cards,
Ethernet cards and Token Ring cards. It is fully compatible with Novell
NetWare and Microsoft LAN Manager and also with SCO UNIX,
XENIX and OS/2 operating systems.
The system has a number of software-controlled security features.
These include power-on password, disk drive read/write control,
diskette boot control, serial- and parallel-port control, and a system
setup control.
Installing options such as memory modules, expansion boards and an
upgrade CPU enhance system performance. This chapter gives step-
by-step instructions on how to install these options.

1-2 User’s Guide
1.1 System Board Layout
The system board has the following major components:
•486SX, SX2, DX2, or DX4 series CPU
•4-MB onboard RAM expandable to 36 MB
•Two 72-pin SIMM sockets for memory upgrade
•128-KB ROM for system BIOS and VGA BIOS
•120-pin connector for ISA riser card
•System clock/calendar
•Two 9-pin serial ports
•One 25-pin Centronics parallel port
•PS/2-compatible keyboard and mouse interface
•512-KB or 1-MB DRAM for onboard local bus VGA interface;
expandable to 1 MB (for GD-5424) or 2 MB (for GD5429)
•Embedded fixed disk interface
•Upgradable cache memory (128-KB or 256-KB)
•Optional enhanced IDE interface
•Optional power daughter board that enables the system to
support the 3.3V microprocessors
Figure 1-1 shows the board layout and the locations of the important
components.

System Board 1-3
1. Keyboard controller 17. Power daughter board
2. M5105 super I/O controller 18. M1429G system chip
3. System and VGA BIOS 19. Onboard memory (4 MB)
4. RTC Battery 20. SIMM sockets
5. Power connector 21. VGA feature connector
6. IDE fixed disk connector #2* 22. VGA connector
7. IDE fixed disk connector #1 23. Parallel port
8. Diskette drive connector 24. COM2 port
9. ISA riser card connector 25. COM1 port
10. Local bus IDE controller* 26. PS/2 mouse connector
11. M1431 system chip 27. PS/2 keyboard connector
12. Second-level cache* 28. VGA upgrade sockets (1 MB)
13. Power daughter board connectors 29. VGA upgrade sockets (2 MB)
14. TAG RAM 30. Onboard VGA memory (512 KB)
15. Fan power connector 31. VGA chip
16. 486 CPU socket
Figure 1-1 System Board Layout
*Optional

1-4 User’s Guide
1.2 ESD Precautions
Electrostatic discharge (ESD) can damage your processor, disk drives,
expansion boards, and other components. Always observe the
following precautions before you install a system component.
1. Do not remove a component from its protective packaging until
you are ready to install it.
2. Wear a wrist grounding strap and attach it to a metal part of the
system unit before handling components. If a wrist strap is not
available, maintain contact with the system unit throughout any
procedure requiring ESD protection.
Integrated circuits are extremely susceptible
to electrostatic discharge. Do not handle ICs
unless you are a qualified service technician,
using tools and techniques that conform to
accepted industry practices.
1.3 Pre-installation Instructions
Follow these steps before you install a system component:
1. Turn off the system power and all the peripheral devices
connected to the unit before you open it.
2. Open the system according to the instructions in the housing
installation manual.
3. Follow the ESD precautions in section 1.2 before handling a
system component.
4. Remove any expansion boards or peripherals that block access
to the SIMM sockets or CPU socket.
5. See the following sections for specific instructions on the
component that you wish to install.

System Board 1-5
Do not attempt the procedures described in
the following sections unless you are a
qualified service technician.
1.4 Jumper Settings
Figure 1-2 shows the jumper locations.
Figure 1-2 Jumper Locations

1-6 User’s Guide
The following tables list the jumper settings and their correponding
functions.
Table 1-1 System Board Jumpers
Jumper Setting Function
JP2 1-2
2-3 Enable password check Bypass password
JP14 Closed
Open Enable onboard VGA Disable onboard VGA
JP16 Open
Closed Enable onboard local bus IDE Disable onboard local bus IDE
JP21 Closed
Open Enable onboard super I/O chip Disable onboard syper I/O chip
JP28 1-2
2-3 Enable onboard memory Disable onboard memory
JP37-38 1-2
2-3 Enable Reset button Enable Suspend/Resume button
Table 1-2 CPU Clock Selection
JP10 JP17 JP19 CN14 CPU Clock
2-3 2-3 2-3 3-7 33 MHz (for SX/33,
DX2/66 or DX4/100)
2-3 2-3 2-3 4-8 25 MHz (for SX2/50
or DX2/50)

System Board 1-7
Table 1-3 CPU Type Selection
4861486 WB2Pentium
OverDrive AMD 486/DX2 AMD 486/DX4 Cyrix IBM TI
JP11 1-2 1-2 1-2 1-2 1-2 2-3 2-3
JP12 1-2 2-3 2-3 1-2 1-2 1-2 2-3
JP13 1-2 1-2 1-2 1-2 1-2 1-2 2-3
JP18 2-3 1-2 1-2 2-3 2-3 2-3 2-3
JP20 2-3 2-3 2-3 2-3 2-3 1-2 2-3
JP30-32 Open Open Open Open Open Closed Open
JP33 1-2 1-2 1-2 1-2 1-2 2-3 1-2
JP34-36 Closed Closed Closed Open Open Open Open
JP39 1-2, 4-5 1-2, 4-5 1-2, 4-5 1-2, 4-5 1-2, 4-5 1-2, 4-5 2-3, 5-6
JP40-41 2-3 2-3 2-3 1-2 1-2 2-3 2-3
JP42 2-3 2-3 2-3 2-3 2-3 2-3 1-2
JP43 Open Open Open Open Open Open Open
JP46 1-2 2-3 2-3 1-2 1-2 1-2 1-2
JP47 1-2 1-2 1-2 1-2 1-2 2-3 1-2
JP48 Open Open Open Closed Open Open Open
Table 1-4 Cache RAM Size Selection
JP24 JP25 JP26 Cache Size
Open Closed 1-2 128 KB
Closed Closed 2-3 256 KB
1Intel 486SX, SX2, DX, DX2 and DX4
2Intel 486DX2 and DX4 with write-back internal cache

1-8 User’s Guide
1.5 Installing Memory
The system board has two 72-pin SIMM sockets that accept 1-MB, 2-
MB, 4-MB, 8-MB, or 16-MB memory modules with 80 ns (or less)
DRAM speed. The maximum system memory size is 36 MB.
When installing additional memory, choose one of the SIMM
configurations listed in Table 1-5.
Table 1-5 Memory Configurations
Onboard Socket 1 Socket 2 Total
4 MB 4 MB
4 MB 1 MB 5 MB
4 MB 1 MB 1 MB 6 MB
4 MB 1 MB 2 MB 7 MB
4 MB 4 MB 8 MB
4 MB 4 MB 1 MB 9 MB
4 MB 4 MB 2 MB 10 MB
4 MB 4 MB 4 MB 12 MB
4 MB 4 MB 8 MB 16 MB
4 MB 16 MB 20 MB
4 MB 16 MB 1 MB 21 MB
4 MB 16 MB 2 MB 22 MB
4 MB 16 MB 4 MB 24 MB
4 MB 16 MB 8 MB 28 MB
4 MB 16 MB 16 MB 36 MB

System Board 1-9
1.5.1 Installing a SIMM
Observe ESD precautions when installing
SIMMs. See section 1.2.
Follow these steps to install a SIMM:
1. Insert the SIMM into the socket at a slight angle, making sure that
the cut edge of the SIMM touches the base of the circle mark on
the SIMM socket.
2. Gently press the SIMM back against the holding clips on both
ends of the socket until the peg slips into the holes on the SIMM,
and the holding clips lock the SIMM into position. See Figure 1-3.
3. Check that the SIMM is securely seated in its slot and that both
ends are locked to the socket.
Figure 1-3 Installing a SIMM

1-10 User’s Guide
1.5.2 Removing a SIMM
Observe ESD precautions when removing
SIMMs. See section 1.2.
1. Press the holding clips on both sides of the SIMM outward to
release it.
2. Push the SIMM upward.
3. Gently pull the SIMM out of the socket.
Figure 1-4 Removing a SIMM
1.5.3 Reconfiguring the System
The system automatically detects the amount of memory installed.
Run Setup to view the new value for total system memory and make a
note of it.

System Board 1-11
1.6 Upgrading the CPU
Conventional technology places the CPU on the same board as the
ISA bus logic, system memory and I/O interface. The entire system
board must be replaced to upgrade the CPU. Single-chip upgrade
technology gives you the flexibility to upgrade the CPU by simply
inserting a new CPU without replacing the entire system board.
1.6.1 Unpacking the Upgrade CPU
Unpack all items and inspect the contents. If any of the following
items are damaged or missing, contact your dealer immediately.
•Upgrade CPU with heat sink
•Electrostatic discharge (ESD) gloves
1.6.2 Installing an Upgrade CPU
Observe ESD precautions when installing
components. See section 1.2.
Before installing an upgrade CPU, check the following:
•The heat sink is not oily
•The heat sink is well attached to the CPU
The heat sink protects the CPU against excessive heat.
Follow these steps to install an upgrade CPU:
1. Turn off the system power.
2. Open the system and locate the CPU socket on the system
board. Refer to Figure 1-1 for location of the CPU socket.
3. Remove the CPU installed in the upgrade socket, if any.

1-12 User’s Guide
4. Insert the upgrade CPU (with the heatsink) into the upgrade
socket. Make sure that pin 1 of the CPU corresponds to hole 1 of
the upgrade socket (see Figure 1-6). The flat corner on the CPU
indicates pin 1. Insert the CPU pins into the socket pinholes
gently but firmly. Be careful not to bend any pins.
Figure 1-5 Pin 1 Indicator on the Upgrade CPUand Socket
Figure 1-6 Installing an Upgrade CPU
5. Set the required jumpers on the system board. Refer to section
1.4 for the jumper settings.
Pin 1 Indicator Pin 1 Indicator
(flat corner)

System Board 1-13
1.7 Power Daughter Board
The power daughter board enables the system to support a 3.3V
microprocessor. Without this board, your system can only support a
5V CPU.
Follow these steps to install the power daughter board:
Before installing, you must check first the
voltage requirement of your upgrade CPU.
1. Locate the power daughter board connectors marked as JP44
and JP45 on the system board. See Figure 1-1.
2. If your system board comes with a 5V CPU, then you will find
JP45 closed. Remove the jumper cap of JP45 and insert the
board into the connectors.

1-14 User’s Guide
1.8 Upgrading VGA Memory
Observe ESD precautions when installing
components. See section 1.2.
The VGA memory is upgradable to 1 or 2 MB depending on your
onboard VGA chip. The system board may come with either a GD-
5424 or a GD-5429 VGA chip. If your board has a GD-5424, then your
VGA memory is expandable to 1 MB only. If your system board has a
GD-5429 VGA chip, then you can further expand your VGA memory to
2 MB. The additional memory allows your VGA to display higher
resolutions and more colors when the appropriate VGA driver is used.
Follow these steps to upgrade the VGA RAM to 1 MB:
1. Locate the VGA memory expansion sockets on the system board
labeled U12, U13, U15 and U16. See Figure 1-7.
2. Gently but firmly insert a 44256 DRAM (256 Kb x 4, 70 ns DIP)
chip into each of the VGA memory expansion sockets.
To upgrade the VGA RAM to 2 MB:
1. Locate sockets U9 and U10 on the system board.
2. Insert a 512460 (256 Kb x 16, 70 ns ZIP) DRAM chip into each
socket. See Figure 1-7.

System Board 1-15
U12 U13 U15 U16
U9
U10
514260 DRAM 44256 DRAM
Figure 1-7 Installing VGA RAM
You do not need to change any jumper settings
when upgrading the VGA memory.

1-16 User’s Guide
1.9 Upgrading Cache Memory
To install cache chips, do the following:
1. Locate the cache sockets on the system board. See Figure 1-1.
2. Align the cut edge of the chip with the cut edge of the cache
sockets. See Figure 1-8.
TAG U56 U57 U58 U59 U60 U61 U62 U63
Figure 1-8 Installing Cache
3. Gently but firmly insert a 32 Kb x 8, 15 ns SRAM chip into each of
the sockets. Be careful not to bend any pins. Table 1-6 lists the
cache size options and the corresponding chip configuration.
Table 1-6 Cache Size Options and Chip Locations
Cache Size SRAM Type Location
128 KB 32 Kb x 8 x 5 pcs TAG, U56, U58, U60, U62
256 KB 32 Kb x 8 x 9 pcs TAG, U56 to U63

System Board 1-17
The SRAM must have an access speed of 15
nanoseconds.
Make sure that you set the jumpers properly.
See section 1.4.
1.10 Post-installation Instructions
Always observe the following:
1. See to it that the components are installed according to the step-
by-step instructions in their respective sections.
2. Make sure you have set all the required jumpers before you
proceed. See section 1.4 for the correct jumper settings.
3. Replace any expansion boards or peripherals that you removed
earlier.
4. Replace the system cover.
5. Connect the necessary cables and turn on the system.

1-18 User’s Guide
1.11 Power-Management Feature
The mainboard incorporates the latest power-conservation technology.
However, to take advantage of its energy-saving capabilities, the
mainboard must have an Intel SL-Enhanced or a power-saving CPU.
The Power-Management feature allows you to monitor system activity.
System activity refers to any action involving one or more of the
following devices: keyboard, mouse, diskette drives, fixed disk drives,
connected peripherals, or video memory. If no activity is detected
within a specified period of time (the inactivity time-out), the system
switches to one of the power-saving modes to conserve energy.
The Setup utility allows you to specify the
inactivity time-out. Refer to Section 2.4 for
more information on the power-saving
configuration.
The power-management function does not
work when the cursor is emulated by
software such as Winword, ETU 3.1
(Chinese system), DOSV (Japanese
system), etc.
The system supports four power-management modes:
•Monitor power-saving mode
•IDE fixed disk standby mode
•Standby mode
•Suspend mode
MONITOR POWER-SAVING MODE
The Monitor Power-Saving Mode offers a quick-resume power-saving
mode for VESA DPMS-compliant VGA monitors. It allows temporary
power saving during operation.

System Board 1-19
Set the independent power-management timers for the VESA DPMS
monitor. Valid values are from 1 to 15 minutes. Any video or I/O
action returns the system to full power.
IDE FIXED DISK STANDBY MODE
The IDE Fixed Disk Standby Mode offers a quick-resume power-
saving mode for ATA-compliant IDE fixed disks. It is allows temporary
power saving during operation.
Set the independent power-management timers for the fixed disk.
Valid values are from 1 to 15 minutes. In this mode, the fixed disk
spin motor is shut off. Any fixed disk activity returns the fixed disk to
normal speed within 3 to 5 seconds (depending on the fixed disk in
use).
SYSTEM STANDBY MODE
This is a fast-on power-saving mode that allows quick-resume
response time and at the same time lowers power-consumption. It is
most suitable for users who want power-saving features but need the
PC to resume normal operation quickly.
Set the Standby Mode timer to a value from 2 to 120 minutes. When
the system enters Standby mode, the turbo LED light on the front
panel starts to blink. Any mouse/keyboard or I/O action enables the
system to exit Standby mode and return quickly to normal operation.
SUSPEND MODE
This mode sends the CPU and all peripherals into the lowest
power-consumption mode possible. However, it takes a longer time
for the system to resume normal operation depending on the fixed disk
drive and monitor type in use.

1-20 User’s Guide
Set the Suspend Mode timer to a value from 2 to 120 minutes, or
activate the Suspend/Resume button. In Suspend mode, the turbo
LED light on the front panel blinks at a rate slower than when the
system is in the Standby mode. Activating the Suspend/Resume
button produces two beeps as the system enters the suspend mode.
Any keyboard/mouse or I/O action resumes full power.
Power-Management Modes
Table 1-7 Power-Management Modes
Monitor
Power-
Saving Mode
IDE Fixed
Disk Standby
Mode
System
Standby
Mode
System
Suspend
Mode
Monitor Mode
Suspend No effect Off On
IDE HDD
Status
No effect Standby
mode
Spindle
motor off
Standby
mode
Spindle
motor off
Standby
mode
Spindle
motor off
CPU/System
Status
Normal Normal Normal CPU clock
stopped
Entry Mode
Device idle
timer time-out
(1 - 15 min)
Device idle
timer time-out
(1 - 15 min)
System
standby timer
time-out
(2 - 120 min)
System
Suspend
timer time-out
(2 - 120 min)
or Suspend
button
pushed
Resume Mode
Device
activated Any fixed disk access Any system event Keyboard/ mouse or
Resume
button
pushed
Resume
Recovery
Time
3 - 5 sec 3 - 5 sec 7 - 10 sec 7 - 10 sec
Application Condition
You must disable the Suspend mode for LAN workstations. Since the
CPU is stopped in Suspend mode, this prevents the workstation from
responding to LAN requests. Thus, the system is considered
disconnected from the network.