Asus P5A-B User manual

R
P5A-B
Pentium®Super7 Motherboard
USER’S MANUAL

2ASUS P5A-B User’s Manual
USER'S NOTICE
No part of this manual, including the products and software described in it, may be repro-
duced, transmitted, transcribed, stored in a retrieval system, or translated into any language in
any form or by any means, except documentation kept by the purchaser for backup purposes,
without the express written permission of ASUSTeK COMPUTER INC. (“ASUS”).
ASUS PROVIDES THIS MANUAL “AS IS” WITHOUT WARRANTY OF ANY KIND, EI-
THER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
WARRANTIES OR CONDITIONS OF MERCHANTABILITY OR FITNESS FOR A PAR-
TICULAR PURPOSE. IN NO EVENT SHALLASUS, ITS DIRECTORS, OFFICERS, EM-
PLOYEES ORAGENTS BE LIABLE FORANYINDIRECT, SPECIAL, INCIDENTAL, OR
CONSEQUENTIALDAMAGES(INCLUDINGDAMAGESFORLOSSOFPROFITS,LOSS
OF BUSINESS, LOSS OF USE OR DATA, INTERRUPTION OF BUSINESS AND THE
LIKE), EVEN IF ASUS HAc BEEN ADVISED OF THE POSSIBILITY OF SUCH DAM-
AGES ARISING FROMANY DEFECT OR ERROR IN THIS MANUAL OR PRODUCT.
Product warranty or service will not be extended if: (1) the product is repaired, modified or
altered, unless such repair, modification of alteration is authorized in writing byASUS; or (2)
the serial number of the product is defaced or missing.
Products and corporate names appearing in this manual may or may not be registered trade-
marks or copyrights of their respective companies, and are used only for identification or
explanation and to the owners’ benefit, without intent to infringe.
• ALi and Aladdin are trademarks of Acer Laboratories Inc. (ALi)
• Adobe and Acrobat are registered trademarks of Adobe Systems Incorporated.
• Intel, LANDesk, and Pentium are registered trademarks of Intel Corporation.
• Windows and MS-DOS are registered trademarks of Microsoft Corporation.
The product name and revision number are both printed on the product itself. Manual revi-
sions are released for each product design represented by the digit before and after the period
of the manual revision number. Manual updates are represented by the third digit in the manual
revision number.
Forprevious or updated manuals, BIOS, drivers, or productrelease information, contactASUS
at http://www.asus.com.tw or through any of the means indicated on the following page.
SPECIFICATIONS AND INFORMATION CONTAINED IN THIS MANUAL ARE FUR-
NISHED FOR INFORMATIONAL USE ONLY, AND ARE SUBJECT TO CHANGE AT
ANY TIME WITHOUT NOTICE, AND SHOULD NOT BE CONSTRUED AS A COM-
MITMENT BY ASUS. ASUS ASSUMES NO RESPONSIBILITY OR LIABILITY FOR
ANYERRORS OR INACCURACIESTHATMAYAPPEARINTHISMANUAL, INCLUD-
ING THE PRODUCTSAND SOFTWARE DESCRIBED IN IT.
Copyright © 1998 ASUSTeK COMPUTER INC. All Rights Reserved.
Product Name: ASUS P5A-B
Manual Revision: 1.03 E264
Release Date: August 1998

ASUS P5A-B User’s Manual 3
ASUS CONTACT INFORMATION
ASUSTeK COMPUTER INC.
Marketing
Address: 150 Li-Te Road, Peitou, Taipei, Taiwan 112
Telephone: [phone]
Fax: [phone]
Email: [email protected]
Technical Support
Fax: [phone]
BBS: [phone]
Email: [email protected]
WWW: www.asus.com.tw
FTP: ftp.asus.com.tw/pub/ASUS
ASUS COMPUTER INTERNATIONAL
Marketing
Address: 6737 Mowry Avenue, Mowry Business Center, Building 2
Newark, CA 94560, USA
Fax: [phone]
Email: [email protected]
Technical Support
Fax: [phone]
BBS: [phone]
Email: [email protected]
WWW: www.asus.com
FTP: ftp.asus.com.tw/pub/ASUS
ASUS COMPUTER GmbH
Marketing
Address: Harkort Str. 25, 40880 Ratingen, BRD, Germany
Telephone: [phone]
Fax: [phone]
Email: [email protected]
Technical Support
Hotline: [phone]
BBS: 49-2102-448690
Email: [email protected]
WWW: www.asuscom.de
FTP: ftp.asuscom.de/pub/ASUSCOM

4ASUS P5A-B User’s Manual
CONTENTS
I. INTRODUCTION........................................................................... 7
How this Manual is Organized ........................................................ 7
Item Checklist .................................................................................. 7
II. FEATURES .................................................................................... 8
ASUS P5A-B Motherboard ............................................................. 8
Introduction to ASUS Smart Series of Motherboards .......... 9
Parts of the ASUS P5A-B Motherboard .......................................... 11
III. INSTALLATION .......................................................................... 12
ASUS P5A-B Motherboard Layout ................................................. 12
Installation Steps.............................................................................. 14
1. Jumpers ........................................................................................ 14
Jumper Settings .................................................................... 15
Compatible Cyrix CPU Identification .................................. 18
2. System Memory (DIMM) ............................................................ 19
DIMM Memory Installation Procedures: ............................. 20
3. Central Processing Unit (CPU)................................................... 21
4. Expansion Cards ......................................................................... 23
Expansion Card Installation Procedure: ............................... 23
Assigning IRQs for Expansion Cards................................... 23
Assigning DMA Channels for ISA Cards............................. 24
ISA Cards and Hardware Monitor........................................ 24
Accelerated Graphics Port .................................................... 24
5. External Connectors.................................................................... 25
Power Connection Procedures ................................................... 35
IV. BIOS SOFTWARE ....................................................................... 36
Support Software ............................................................................. 36
Flash Memory Writer Utility...................................................... 36
Main Menu ........................................................................... 36
Managing and Updating Your Motherboard’s BIOS.................. 38
6. BIOS Setup ................................................................................. 39
Load Defaults ....................................................................... 40
Standard CMOS Setup ............................................................... 40
Details of Standard CMOS Setup......................................... 40
BIOS Features Setup .................................................................. 43
Details of BIOS Features Setup............................................ 43
Chipset Features Setup ............................................................... 46
Details of Chipset Features Setup......................................... 46
Power Management Setup.......................................................... 49
Details of Power Management Setup ................................... 49

ASUS P5A-B User’s Manual 5
CONTENTS
PNP and PCI Setup .................................................................... 52
Details of PNP and PCI Setup .............................................. 52
Load BIOS Defaults ................................................................... 54
Load Setup Defaults ................................................................... 54
Supervisor Password and User Password .................................. 55
IDE HDD Auto Detection .......................................................... 56
Save & Exit Setup ...................................................................... 57
Exit Without Saving ................................................................... 57
V. SUPPORT SOFTWARE................................................................ 59
ASUS Smart Motherboard Support CD 5.01................................... 59
Desktop Management Interface (DMI)............................................ 60
Introducing the ASUS DMI Configuration Utility ............... 60
System Requirements ........................................................... 60
Using the ASUS DMI Configuration Utility ........................ 61
VI. ASUS LAN Card .......................................................................... 63
ASUS PCI-L101 Fast Ethernet Card ............................................... 63
Features ............................................................................................ 64
Software Driver Support ............................................................ 64
Question and Answer ................................................................. 64

6ASUS P5A-B User’s Manual
FCC & DOC COMPLIANCE
FederalCommunications CommissionStatement
This device complies with FCC Rules Part 15. Operation is subject to the following
two conditions:
• This device may not cause harmful interference, and
• This device must accept any interference received, including interference that
may cause undesired operation.
This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference in a residential installa-
tion. This equipment generates, uses and can radiate radio frequency energy and, if
not installed and used in accordance with manufacturer’s instructions, may cause
harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment does cause
harmful interference to radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try to correct the interfer-
ence by one or more of the following measures:
• Re-orient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment to an outlet on a circuit different from that to which the
receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.
WARNING! The use of shielded cables for connection of the monitor to the
graphics card is required to assure compliance with FCC regulations. Changes
or modifications to this unit not expressly approved by the party responsible for
compliance could void the user’s authority to operate this equipment.
CanadianDepartment ofCommunications Statement
This digital apparatus does not exceed the Class B limits for radio noise emissions
from digital apparatus set out in the Radio Interference Regulations of the Canadian
Department of Communications.

ASUS P5A-B User’s Manual 7
I. INTRODUCTION
I. INTRODUCTION
Sections/Checklist
How this Manual is Organized
I. Introduction Manual information and checklist
II. Features Information and specifications concerning this product
III. Installation Instructions on setting up the motherboard
IV. BIOS Software Instructions on setting up the BIOS software
V. Support Software Information on the included support software
VI. ASUS L101 Card Installation of the ASUS LAN card (optional)
Item Checklist
Please check that your package is complete. If you discover damaged or missing
items, contact your retailer.
(1) ASUS Motherboard
(2) 9pin male serial external connector set
(1) 25pin female parallel + 6pin female PS/2 mouse external connector set
(1) IDE ribbon cable for master and slave drives
(1) Floppy ribbon cable for (1) 5.25inch and (2) 3.5inch floppy disks
(1) bag of spare jumpers
(1) CD disc with support drivers and utilities
• Flash Memory Writer utility to update the onboard programmable BIOS
• Desktop Management Interface (DMI) utility
• Bus Master IDE Drivers for various operating systems
• PC-Cillin Lite
• Intel LDCM Utility (optional)
• ASUS PC Probe Utility
• ALi
®
AGP Mini Port Driver for Windows 95/Windows 98
• ALi
®
M7101 Patch for Windows 95
• Audio chipset drivers (optional)
• Readme files for descriptions and use of the files
• Technical Support Form
(1) User’s Manual
Audio Bracket (optional; available with ISA audio option)
PS/2 Mouse, Infrared, USB1, and USB2 external connector module (optional)
ASUS PCI-L101 Wake-on-LAN 10/100 Ethernet Card (optional)

8ASUS P5A-B User’s Manual
II. FEATURES
Features
II. FEATURES
ASUS P5A-B Motherboard
•ALi AGPset: ALi®(Acer Laboratories Inc.) Aladdin V AGPset with support for a
100MHz Front Side Bus (FSB), Accelerated Graphics Port (AGP), and all current
Socket-7 processors.
•Multi-Processor/Multi-Speed Support: AMD-K6™-2 (PR266–PR350), AMD-
K6™(PR166 & faster),AMD-K5™(PR75–PR133), IBM®/Cyrix®6x86MX™/M II™
(PR166 & faster), IBM®/Cyrix®6x86-PR166+ (Rev 2.7 or later), Intel Pentium®
75–233MHz (P55C-MMX™).
•EnhancedACPI and Anti-Boot Virus BIOS: Features a programmable BIOS, offer-
ing enhanced ACPI for Windows 98 compatibility, built-in hardware-based virus pro-
tection through Trend ChipAwayVirus, and autodetection of most devices for virtually
automatic setup.
•PC/100 Memory Support: Equipped with three DIMM sockets to support Intel
PC/100-compliant SDRAMs (8, 16, 32, 64, 128, or 256MB) up to 768MB. These
new SDRAMs are necessary to meet the 95MHz/100MHz bus speed requirement.
•AGPSlot: SupportsAGPcards for high performance, component level interconnec-
tion targeted at 3D graphical display applications.
•Ultra DMA/33 BM IDE: Comes with an onboard PCI Bus Master IDE controller
with two connectors that supports four IDE devices in two channels, supports Ultra
DMA/33, PIO Modes 3 and 4 and Bus Master IDE DMA Mode 2, and supports
Enhanced IDE devices, such as Tape Backup and CD-ROM drives. Supports two
drives of either 5.25-inch (360KB or 1.2MB) or 3.5-inch (720KB, 1.44MB, or
2.88MB) disk drives. Supports Japanese “Floppy 3 mode” (3.5-inch disk drive:
1.2MB)andLS-120 floppy disk drives (3.5-inch disk drive: 120 MB, 1.44MB, 720K).
BIOS supports IDE CD-ROM or SCSI device boot-up.
•Wake-on-LAN: Supports Wake-on–LAN activity with special network cards, such
as the ASUS PCI-L101 10/100 Fast Ethernet PCI card.
•ISA Audio (optional): Features C-Media’s 3D positional sound chip, which pro-
vides such cutting edge features as wavetable music synthesizer, 3D surround audio,
and SPDIF I/O interface aside from the usual compatibility with games written for
both Windows®95 and DOS®.
• Super Multi-I/O: Provides two high-speed UART compatible serial ports and one
parallelport with EPPand ECPcapabilities. UART2 can also be directedfrom COM2
to the Infrared Module for wireless connections.
• Desktop Management Interface (DMI): Supports DMI through BIOS, which al-
lows hardware to communicate within a standard protocol creating a higher level of
compatibility. (Requires DMI-enabled components.) (See section V)
•Level2CacheSRAM/TagRAM:Supports512KB/1024KBpipelined-burstSRAM/L2
memory cache and integrated Tag RAM to make using the 100MHz bus speed possible.
•USB, PS/2 Mouse, IrDA Connector: Supports an optional cable and bracket set to
mount the connectors to an unused expansion slot on the system chassis. A second
IrDA connector is available for a standard individual infrared cable set.

ASUS P5A-B User’s Manual 9
II. FEATURES
II. FEATURES
Smart Series
Introduction to ASUS Smart Series of Motherboards
Performance
• SDRAM Optimized Performance: ASUS Smart Series of motherboards sup-
port the new generation memory—Synchronous Dynamic Random Access
Memory (SDRAM)—which increases the data transfer rate from 264MB/sec
maximum using EDO memory to 528MB/sec max using SDRAM.
• Double the IDE Transfer Speed: ASUS Smart Series of motherboards with
ALi’s Aladdin V chipset improves IDE transfer rate using UltraDMA/33 Bus
Master IDE, which can handle data transfer up to 33MB/sec. The best of all is
that this new technology is compatible with existing ATA-2 IDE specifications
so there is no need to upgrade current hard drives or cables.
•Concurrent PCI: Concurrent PCI allows multiple PCI transfers from PCI mas-
ter buses to memory to CPU.
• ACPIReady:ACPI(AdvancedConfiguration and PowerInterface)isalso imple-
mented on allASUS Smart Series of motherboards.ACPI provide more Energy
Saving Features for the future operating systems (OS) supporting OS Direct
Power Management (OSPM) functionality. With these features implemented in
the OS, PCs can be ready around the clock, yet satisfy all the energy saving
standards. To fully utilize the benefits ofACPI, an OS that supports ACPI, such
as Windows 98, must be used.
• PC’98 Compliant: Both the BIOS and hardware levels of the ASUS smart
motherboard series meet PC’98 compliancy. The new PC’98 requirements for
systems and components are based on the following high-level goals: Support
for Plug and Play compatibility and power management for configuring and
managing all system components, and 32-bit device drivers and installation pro-
cedures for Windows 95/Windows 98 and Windows NT.
Intelligence (with optional Hardware Monitor only)
• Fan Status Monitoring and Alarm: To prevent system overheat and system
damage, the CPU fan and system fans are monitored for RPM and failure. Each
fan can be set for its normal RPM range and alarm thresholds.
•Temperature Monitoring and Alert: To prevent system overheat and system
damage, there is a heat sensor under the CPU and on the motherboard itself to
monitor CPU and system temperature to make sure the system is operating at a
safe heat level to avoid any failures triggered by extremely high temperature.

10 ASUS P5A-B User’s Manual
II. FEATURES
P5A-B Series
II. FEATURES
•Voltage Monitoring and Alert: System voltage levels are monitored to ensure
stable current to critical motherboard components. Voltage specifications are
more critical for future processors, so monitoring is necessary to ensure proper
system configuration and management.
• SystemResourcesAlert:Today’s operating systems, such as Windows 95,Win-
dows NT, and OS/2, require much more memory and hard drive space to present
enormous user interfaces and run large applications. The system resource moni-
tor will warn the user before the system resources are used up to prevent pos-
sible application crashes. Suggestions will give the user information on manag-
ing their limited resources more efficiently.
• CPU Slow Down: When CPU fans or system fans are malfunctioning, the sys-
tem will deactivate the CPU Clock line to decrease CPU utilization to the speed
upon detection of system overheat. This will prevent CPU damage from system
overheat. The CPU utilization will restore normal operations when temperature
falls below a safe level.
• Auto Fan Off: The system fans will power off automatically even in sleep
mode.This function reduces both energy consumption and system noise, and is
a important feature to implement silent PC systems.
• Dual Function Power Button (requires ATX power supply): The system can
be in one of two states, one is Sleep mode and the other is Soft-Off mode. Pushing
the power button for less than 4 seconds places the system into Sleep mode.When
the power button is pressed for more than 4 seconds, it enters the Soft-Off mode.
• Remote Ring On (requiresATX power supply):This feature allows a computer
to be turned on remotely through a modem. With this benefit on hand, any user
can access vital information from their computer from anywhere in the world!
• Message LED (requires ACPI-supported OS): Chassis LEDs now act as in-
formation providers. Through the way a particular LED illuminates, the user
can determine the stage the computer is in. A simple glimpse provides useful
information to the user.

ASUS P5A-B User’s Manual 11
Parts of the ASUS P5A-B Motherboard
II. FEATURES
II. FEATURES
Motherboard Parts
512KB/1024KB
Pipelined Burst L2
Cache
CPU ZIF
Socket 7
3 PCI Slots
USB/MIR
Programmable
Flash ROM
2ISA Slots
Floppy/IDE
Connectors
Serial
Ports 3 DIMM
Sockets
IrDA
ATX Power
Accelerated
Graphics Port
Parallel
Port
Keyboard
ALi Aladdin V
AGPset AT Connector
C-Media 3D
Positional
Sound Chip
(optional)

12 ASUS P5A-B User’s Manual
III. INSTALLATION
ASUS P5A-B Motherboard Layout
Motherboard Layout
III. INSTALLATION
R
Accelerated Graphics Port
PCI Slot 1
PCI Slot 2
ISA Slot 1
ISA Slot 2
C-Media
3D Positional
Sound Chip
(optional)
IDELED
ATX Power Connector
ALi
Aladdin V
AGPset
CD2
CD1
1Mbit Flash EEPROM
(Programmable BIOS)
CHA_FAN
IR
Panel Connectors
SPDI
Secondary IDE
Primary IDE
Floppy Drive
DIMM Socket 1 (64-bit, 168-pin module)
DIMM Socket 2 (64-bit, 168-pin module)
Row 10
32
ALi
M1543
Chip
CR2032 3V
Lithium Cell
PCI Slot 3
SPDO
TTL
CPU_FAN
DIMM Socket 3 (64-bit, 168-pin module)
54
VID1
VID0
VID2
PWR_FAN
BF1
BF0
BF2
FS1
FS0
FS2
FS3
VIO1
VIO0
AUX
VID3
CLRTC
+
AT Power Connector
WOLCON
Chassis Intrusion Alarm Lead
SMBus Connector
Audio Connectors
Temp Sensor
USB, PS/2 Mouse,
IrDA
COM 1
Parallel Port
COM 2
AT
Keyboard
Connector
CPU ZIF Socket 7
512KB/
1024KB
Pipelined
Burst L2
Cache
KB

ASUS P5A-B User’s Manual 13
III. INSTALLATION
Jumpers
1) CLRTC p. 15 Real Time Clock (RTC) RAM
2) VIO p. 15 Voltage Input/Output Selection
4) FS0, FS1, FS2, FS3 p. 16 CPU External (BUS) Frequency Selection
5) BF0, BF1, BF2 p. 16 CPU to BUS Frequency Ratio
6) VID0, VID1, VID2, VID3 p. 18 Voltage Regulator Output Selection
Expansion Slots
1) DIMM Sockets p. 19 168-Pin DIMM Memory Expansion Sockets
2) CPU ZIF Socket 7 p. 21 Central Processing Unit (CPU) Socket
3) SLOT 1, 2 p. 23 16-bit ISA Bus Expansion Slots
*
4) PCI 1, 2, 3 p. 23 32-bit PCI Bus Expansion Slots
Connectors
1) KB p. 25 Keyboard Connector (5-pin Female)
2) FLOPPY p. 25 Floppy Drive Connector (34-1 pins)
3) PRINTER p. 26 Parallel (Printer) Port Connector (26-1 pins)
4) COM1, COM2 p. 26 Serial Port COM1 & COM2 (10-1 pins)
5) FAN p. 27 Power Supply, Chassis, CPU Fan Power Leads (3 pins)
6) CHASIS p. 27 Chassis Open Alarm Lead (4-1 pins)
7) PRIMARY/SECOND.IDE p. 28 Primary/Secondary IDE Connector (40-1 pins)
8) IDELED p. 28 IDE LED Activity Light (2 pins)
9) ATX p. 29 ATX Motherboard Power Connector (20 pins)
10) PS/2 p. 29 AT Motherboard Power Connector (12 pins)
11) USB/MIR p. 31 USB, Infrared, PS/2 Mouse Module Connector (18-1 pins)
12) IR p. 31 IrDA/Fast IR-compliant Infrared Module Connector (5 pins)
13) MSG.LED (PANEL) p. 31 System Message LED (2 pins)
14) PWR SW. (PANEL) p. 31 ATX Power Switch/Soft Power Switch Lead (2 pins)
15) RESET (PANEL) p. 31 Reset Switch Lead (2 pins)
16)
PWR.LED ( PANEL ) p. 31 System Power LED Lead (3 pins)
17) KEYLOCK ( PANEL ) p. 31 Keyboard Lock Switch Lead (2 pins)
18) SPEAKER (PANEL) p. 31 Speaker Output Connector (4 pins)
19) WOLCON p. 32 Wake-on-LAN Activity Connector (3 pins)
20) SMB p. 32 SMBus Connector (5-1 pins)
21) AUDIOCON p. 33 Audio Jack Connector (26 pins)
22) SPD0/SPD1/TTL p. 33 DigitalAudio Interface (6 pins)
23) AUX p. 34 Stereo Audio In Connector (4 pins)
24) CD1/CD2 p. 34 Stereo Audio In Connector (4 pins)
*
The onboard hardware monitor uses the address 290H-297H so legacy ISA cards
must not use this address or else conflicts will occur.
Map of Board
III. INSTALLATION

14 ASUS P5A-B User’s Manual
III. INSTALLATION
Jumpers
III. INSTALLATION
Installation Steps
Before using your computer, you must complete the following steps:
1. Set Jumpers on the Motherboard
2. Install System Memory Modules
3. Install the Central Processing Unit (CPU)
4. Install Expansion Cards
5. Connect Ribbon Cables, Cabinet Wires, and Power Supply
6. Setup the BIOS Software
1. Jumpers
Several hardware settings are made through the use of jumper caps to connect jumper
pins (JP) on the motherboard. See motherboard layout for locations of jumpers. The
jumper settings will be described numerically, such as [----], [1-2], [2-3] for no con-
nection, connect pins 1&2, and connect pins 2&3 respectively. Pin 1 for our mother-
boards is always on top
PIN 1
or on the left
PIN 1
when holding the motherboard with
the keyboard connector away from yourself. A“1” is written besides pin 1 on jumpers
with three pins. The jumpers will also be shown graphically such as to connect
pins 1&2 and to connect pins 2&3. Jumpers with two pins will be shown as
for Short (On) and for Open (Off). For manufacturing simplicity, the jump-
ers may be sharing pins from other groups. Use the diagrams in this manual instead of
following the pin layout on the board. Settings with two jumper numbers require that
both jumpers be moved together. To connect the pins, simply place a plastic jumper
cap over the two pins as diagrammed.
WARNING!Computer motherboards, baseboards andcomponents, such as SCSI
cards, contain very delicate Integrated Circuit (IC) chips. To protect them against
damage from static electricity, you should follow some precautions whenever you
work on your computer.
1. Unplug your computer when working on the inside.
2. Use a grounded wrist strap before handling computer components. If you do
not have one, touch both of your hands to a safely grounded object or to a
metal object, such as the power supply case.
3. Hold components by the edges and try not to touch the IC chips, leads or
connectors, or other components.
4. Place components on a grounded antistatic pad or on the bag that came with
the component whenever the components are separated from the system.

ASUS P5A-B User’s Manual 15
III. INSTALLATION
Jumper Settings
1. Real Time Clock (RTC) RAM (CLRTC)
The CMOS RAM is powered by the onboard button cell battery. To clear the
RTC data: (1) Turn off your computer, (2) Short solder points using a small
metalic object, (3)Turn on your computer, (4)Hold down <Delete>during bootup
and enter BIOS setup to re-enter user preferences.
P5A-B Clear RTC RAM
Short solder points
to Clear CMOS
CLRTC
R
III. INSTALLATION
Jumpers
2. Voltage Input/Output Selection (VIO)
This jumper allows you to select the voltage supplied to the DRAM, chipset,
and AGP.
P5A-B Voltage Input/Output Selection
VIO0
VIO1
3.6Volts
VIO0
VIO1
3.8Volts
VIO0
VIO1
4.0Volts
VIO0
VIO1
3.5Volts
(DEFAULT)
1
2
3
R
WARNING! Using a higher voltage may help when overclocking but may re-
sult in the shortening of your computer components’ life.

16 ASUS P5A-B User’s Manual
III. INSTALLATION
Jumpers
III. INSTALLATION
3. CPU External (BUS) Frequency Selection (FS0, FS1, FS2, FS3)
These jumpers tell the clock generator what frequency to send to the CPU. These
allow the selection of the CPU’s External frequency (or BUS Clock). The BUS Clock
timesthe BUS Ratioequalsthe CPU's Internalfrequency (theadvertised CPU speed).
4. CPU to BUS Frequency Ratio (BF0, BF1, BF2)
These jumpers set the frequency ratio between the Internal frequency of the CPU
and the Externalfrequency (called the BUS Clock)within theCPU.These mustbe
set together with the above jumpers CPU External (BUS) Frequency Selection.
CPU External Clock (BUS) Frequency Selection
CPU : BUS Frequency Ratio
3.0x(3/1)
3.0x(3/1)
3.0x(3/1)
—
2.5x(5/2)
2.5x(5/2)
2.5x(5/2)
1.0x(1/1)
2.0x(2/1)
2.0x(2/1)
2.0x(2/1)
2.0x(2/1)
3.5x(7/2)
1.5x(3/2)
3.5x(7/2)
3.0x(3/1)
CPU A
CPU B
CPU C
CPU D
4.0x(4/1)
—
—
—
4.5x(9/2)
—
—
—
Match the “Ratio” column of the table on
the opposite page to these CPU types:
105MHz
70MHz
35MHz
1
2
3110MHz
77.6MHz
38.8MHz
115MHz
77.6MHz
38.3MHz
120MHz
80MHz
40MHz
1
2
3
BF0 BF1 BF2
BF0 BF1 BF2 BF0 BF1 BF2 BF0 BF1 BF2 BF0 BF1 BF2 BF0 BF1 BF2
CPU
AGP
PCI
→
→
→
P5A-B
→
→
→
→
R
60MHz
60MHz
30MHz
1
2
3
FS0 FS1 FS2
66.8MHz
66.8MHz
33.4MHz
75MHz
75MHz
37.5MHz
83.3MHz
66.6MHz
33.3MHz
95MHz
63.3MHz
31.6MHz
100MHz
66.6MHz
33.3MHz
FS0 FS1 FS2
FS0 FS1 FS2
FS0 FS1 FS2
FS0 FS1 FS2
CPU
AGP
PCI
→
→
→
FS3 FS3 FS3
FS3
FS3
5.0x(5/1)
—
—
—
BF0 BF1 BF2
WARNING! Frequencies above 100MHz exceed the specifications for the on-
board chipset and are not guaranteed to be stable. The table on the following
page is for general reference purposes only. Always refer to the instructions in-
cluded with your CPU when possible.
CPU A: AMD-K6-2,AMD-K6
CPU B: Intel Pentium P54C, AMD-K5
CPU C: Intel Pentium P55C, IBM/Cyrix 6x86MX, IBM/Cyrix M II
CPU D: IBM/Cyrix 6x86, IBM/Cyrix 6x86L

ASUS P5A-B User’s Manual 17
III. INSTALLATION
Jumpers
III. INSTALLATION
Setthejumpers by the Internal speedofthe Intel,AMD, IBM, or CyrixCPUas follows:
(BUS Freq.) (Freq. Ratio)
CPU Model Freq. Ratio BUS F. FS0 FS1 FS2 FS3 BF0 BF1 BF2
AMD-K6-2-PR350 350MHz A-3.5x 100MHz [1-2] [1-2] [1-2] [2-3] [1-2] [1-2] [----]
AMD-K6-2-PR333 333MHz A-3.5x 95MHz [2-3] [1-2] [1-2] [2-3] [1-2] [1-2] [----]
AMD-K6-2-PR300 300MHz A-3.0x 100MHz [1-2] [1-2] [1-2] [2-3] [1-2] [2-3] [----]
AMD-K6-2-PR266 266MHz A-4.0x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [1-2] [2-3]
AMD-K6-PR300 300MHz A-4.5x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [2-3] [2-3]
AMD-K6-PR266 266MHz A-4.0x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [1-2] [2-3]
AMD-K6-PR233 233MHz A-3.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
AMD-K6-PR200 200MHz A-3.0x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [2-3] [----]-
AMD-K6-PR166 166MHz A-2.5x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
AMD-K5-PR133 100MHz B-1.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
AMD-K5-PR120 90MHz B-1.5x 60MHz [2-3] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
AMD-K5-PR100 100MHz B-1.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
AMD-K5-PR90 90MHz B-1.5x 60MHz [2-3] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
Intel Pentium P54C 166MHz B-2.5x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
Intel Pentium P54C 150MHz B-2.5x 60MHz [2-3] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
Intel Pentium P54C 133MHz B-2.0x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [1-2] [----]
Intel Pentium P54C 120MHz B-2.0x 60MHz [2-3] [2-3] [2-3] [2-3] [2-3] [1-2] [----]
Intel Pentium P54C 100MHz B-1.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
Intel Pentium P54C 90MHz B-1.5x 60MHz [2-3] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
Intel Pentium P55C 233MHz C-3.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
Intel Pentium P55C 200MHz C-3.0x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [2-3] [----]
Intel Pentium P55C 166MHz C-2.5x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
IBM/CyrixM II-PR333 333MHz C-3.0x 83MHz [1-2] [2-3] [1-2] [2-3] [1-2] [2-3] [----]
IBM/CyrixM II-PR300 300MHz C-3.0x 75MHz [1-2] [1-2] [2-3] [2-3] [1-2] [2-3] [----]
IBM/CyrixM II-PR300 300MHz C-3.5x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [1-2] [----]
IBM/Cyrix6x86MX-PR233 200MHz C-3.0x 66MHz [1-2] [2-3] [2-3] [2-3] [1-2] [2-3] [----]
IBM/Cyrix6x86MX-PR200 166MHz C-2.5x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
IBM/Cyrix6x86MX-PR166 150MHz C-2.5x 60MHz [2-3] [2-3] [2-3] [2-3] [2-3] [2-3] [----]
*IBM/Cyrix 6x86-PR166+ 133MHz D-2.0x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [1-2] [----]
*IBM/Cyrix 6x86L-PR166+ 133MHz D-2.0x 66MHz [1-2] [2-3] [2-3] [2-3] [2-3] [1-2] [----]
*NOTE: The only IBM or Cyrix 6x86(L) (or M1) that is supported on this motherboard is revision 2.7
or later (see next page).

18 ASUS P5A-B User’s Manual
III. INSTALLATION
Jumpers
III. INSTALLATION
5. Voltage Regulator Output Selection (VID0, 1, 2, 3)
These jumpers set the voltage supplied to the CPU. Switching regulators allow
some jumper settings to be the same for two voltages of different power planes.
AMD-K6-2
(PR266 & faster) AMD-K5 (PR75-PR133) IBM/Cyrix 6x86 (M1) (PR166 & faster)
Pentium MMX (P55C)
(150MHz-233MHz)
AMD-K6
(PR166 & faster) IBM/Cyrix 6x86 (M1) (PR166 & faster)
WARNING! Because CPU designs change rapidly, the table below is only in-
tended as a simple guideline and thus may not be true for your CPU. Always
refer to the CPU documentation for your CPU’s voltage and then set the appro-
priate VID jumpers according to the illustration below.
Manufacturer CPU Type Single Plane Dual Plane VID0 VID1 VID2 VID3
AMD (.25micron) K6-233,266,300 ---- 2.2V(Dual) [1-2] [2-3] [1-2] [1-2]
K6-2-266,300,333
AMD K5 3.5V(VRE) ---- [2-3] [2-3] [2-3] [2-3]
IBM/Cyrix 6x86 3.5V(VRE) ---- [2-3] [2-3] [2-3] [2-3]
Intel P54C/P54CS 3.5V(VRE) ---- [2-3] [2-3] [2-3] [2-3]
AMD K5 3.4V(STD) ---- [1-2] [2-3] [2-3] [2-3]
Intel P54C/P54CS 3.4V(STD) --- [1-2] [2-3] [2-3] [2-3]
AMD (.35micron) K6-PR233 ---- 3.2V(Dual) [1-2] [1-2] [2-3] [2-3]
AMD (.35micron) K6-166,200 ---- 2.9V(Dual) [2-3] [1-2] [1-2] [2-3]
IBM/Cyrix 6x86MX ---- 2.9V(Dual) [2-3] [1-2] [1-2] [2-3]
Intel P55C-MMX ---- 2.8V(Dual) [1-2] [1-2] [1-2] [2-3]
Compatible Cyrix CPU Identification
The only Cyrix 6x86-PR166+ CPU that is supported on this
motherboard must be Revision 2.7 or later. Look on the un-
derside of the CPU for the serial number. The number should
read G8DC6620A or later.
P5A-B CPU Vcore Voltage Selection
1
2
3
1
2
3
1
2
3
VID2 VID1 VID0
2.1Volts
VID3
2.2Volts 2.3Volts
2.5Volts 2.7Volts 2.8Volts 2.9Volts
3.0Volts 3.1Volts 3.2Volts 3.3Volts 3.4Volts
3.5Volts
2.0Volts 2.4Volts
2.6Volts
1
2
3
VID2 VID1 VID0 VID3 VID2 VID1 VID0 VID3 VID2 VID1 VID0 VID3 VID2 VID1 VID0 VID3
R

ASUS P5A-B User’s Manual 19
III. INSTALLATION
System Memory
III. INSTALLATION
2. System Memory (DIMM)
This motherboard uses only Dual Inline Memory Modules (DIMMs). Three sockets
are available for 3.3Volt (power level) unbuffered Synchronous Dynamic Random
Access Memory (SDRAM) of either 8, 16, 32, 64, 128MB, or 256MB to form a
memory size between 8MB to 768MB. One side (with memory chips) of the DIMM
takes up one row on the motherboard.
To utilize the chipset’s Error Checking and Correction (ECC) feature, you must use a
DIMM module with 9 chips per side (standard 8 chips/side + 1 ECC chip) and make
the proper settings through “Chipset Features Setup” in BIOS setup.
Memoryspeed setup isrecommended through SDRAMConfigurationunder “Chipset
Features Setup” in BIOS setup.
IMPORTANT (see General DIMM Notes below)
• When using the 95MHz/100MHz bus speed, SDRAMs used must be com-
patible with the current Intel PC/100 SDRAM specification.
Install memory in any combination as follows:
DIMM Location 168-pin DIMM Total Memory
Socket 1 (Rows 0&1) SDRAM 8, 16, 32, 64, 128, 256MB x1
Socket 2 (Rows 2&3) SDRAM 8, 16, 32, 64, 128, 256MB x1
Socket 3 (Rows 4&5) SDRAM 8, 16, 32, 64, 128, 256MB x1
Total System Memory (Max 768MB) =
General DIMM Notes
•Whenusing the 95MHz/100MHzbus speed, useonlyPC/100-compliant DIMMs. Most
systems will not even boot if non-compliant modules are used because of the strict timing
issues involved under this speed.
•Two possible memory chips are supported: SDRAM with and without ECC. ECC is not
supported under the 95MHz/100MHz bus speed .
• SDRAM chips are generally thinner with higher pin density than EDO (Extended Data
Output) chips.
• BIOS shows SDRAM memory on bootup screen.
• 8 chips/side modules do not support ECC, only 9 chips/side modules support ECC.
• Single-sided DIMMs are available in 16, 32, 64, 128MB; double sided in 32, 64, 128, 256MB.
ECC EDO DIMM (9 chips) Non-ECC SDRAM DIMM (8 chips)
ASUS Memory Modules

20 ASUS P5A-B User’s Manual
III. INSTALLATION
System Memory
III. INSTALLATION
DIMM Memory Installation Procedures:
Insert the module(s) as shown. Because the number of pins are different on either
side of the breaks, the module will only fit in the orientation as shown. DRAM
SIMM modules have the same pin contacts on both sides. SDRAM DIMMs have
different pin contacts on each side and therefore have a higher pin density.
P5A-B 168-Pin DIMM Memory Sockets
88 Pins
60 Pins
20 Pins
Lock
R
The DIMMs must be 3.3Volt unbuffered SDRAMs. To determine the DIMM type,
check the notches on the DIMMs (see figure below).
168-Pin DIMM Notch Key Definitions (3.3V)
DRAM Key Position Voltage Key Position
Unbuffered
RFU
Buffered Reserved
3.3V
5.0V
The notches on the DIMM will shift between left, center, or right to identify the type
and also to prevent the wrong type from being inserted into the DIMM slot on the
motherboard. You must tell your retailer the correct DIMM type before purchasing.
This motherboard supports four clock signals per DIMM.