Compaq EN Series Use and care manual

Technical
Reference
Guide
For the
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models

This hardcopy is designed to be placed into a standard 3-ring binder. Provided below is a title block that
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Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
TRG

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
i
NOTICE
The information in this document is subject to change without notice.
COMPAQ COMPUTER CORPORATION SHALL NOT BE LIABLE FOR TECHNICAL OR
EDITORIAL ERRORS OR OMISSIONS HEREIN; NOR FOR INCIDENTAL OR
CONSEQUENTIAL DAMAGES RESULTING FROM THE FURNISHING, PERFORMANCE,
OR USE OF THIS MATERIAL. IT IS THE RESPONSIBILITY OF MANUFACTURERS TO
ENSURE THAT DEVICES DESIGNED TO BE USED WITH COMPAQ PRODUCTS
COMPLY WITH FCC CLASS B EMISSIONS REQUIREMENTS.
This guide contains information protected by copyright. No part of this document may be
photocopied or reproduced in any form without prior written consent from Compaq Computer
Corporation.
1998 Compaq Computer Corporation
All rights reserved. Printed in the USA
Compaq, Deskpro, LTE, Contura, Presario, ProLinea
Registered U.S. Patent and Trademark Office
Product names mentioned in this document may be trademarks and/or registered trademarks of other companies.
“Pentium, ” “Celeron,” and “MMX” are trademarks ofIntel Corporation.
“Windows” is a trademark of Microsoft Corporation.
For more information regarding specifications and Compaq-specific parts please contact Compaq
Computer Corporation, Industry Relations Department.
Technical Reference Guide
for
Compaq Deskpro EN Series of Personal Computers, Net PC and Small Form Factor Models
First Edition – June 1998
Document Number DSK-008A/0698

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
ii

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
iii
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION........................................................................................................1-1
1.1 ABOUT THIS GUIDE ........................................................................................................... 1-1
1.1.1 USING THIS GUIDE.....................................................................................................1-1
1.1.2 ADDITIONAL INFORMATION SOURCES..................................................................1-1
1.2 NOTATIONAL CONVENTIONS..........................................................................................1-2
1.2.1 VALUES........................................................................................................................1-2
1.2.2 RANGES........................................................................................................................1-2
1.2.3 SIGNAL LABELS..........................................................................................................1-2
1.2.4 REGISTER NOTATION AND USAGE .........................................................................1-2
1.2.5 BIT NOTATION............................................................................................................ 1-2
1.3 COMMON ACRONYMS AND ABBREVIATIONS..............................................................1-3
CHAPTER 2 SYSTEM OVERVIEW................................................................................................2-1
2.1 INTRODUCTION.................................................................................................................. 2-1
2.2 FEATURES AND OPTIONS.................................................................................................2-2
2.2.1 STANDARD FEATURES..............................................................................................2-2
2.2.2 OPTIONS.......................................................................................................................2-3
2.3 MECHANICAL DESIGN...................................................................................................... 2-4
2.3.1 CABINET LAYOUTS....................................................................................................2-4
2.3.2 CHASSIS LAYOUT.......................................................................................................2-6
2.3.3 BOARD LAYOUTS.......................................................................................................2-7
2.4 SYSTEM ARCHITECTURE.................................................................................................. 2-8
2.4.1 PENTIUM II PROCESSOR.......................................................................................... 2-10
2.4.2 MEMORY....................................................................................................................2-10
2.4.3 SUPPORT CHIPSET....................................................................................................2-11
2.4.4 MASS STORAGE........................................................................................................ 2-11
2.4.5 SERIAL AND PARALLEL INTERFACES.................................................................. 2-12
2.4.6 UNIVERSAL SERIAL BUS INTERFACE................................................................... 2-12
2.4.7 GRAPHICS SUBSYSTEM........................................................................................... 2-12
2.4.8 AUDIO SUBSYSTEM .................................................................................................2-12
2.5 SPECIFICATIONS..............................................................................................................2-13
CHAPTER 3 PROCESSOR/MEMORY SUBSYSTEM...................................................................3-1
3.1 INTRODUCTION.................................................................................................................. 3-1
3.2 PROCESSOR/MEMORY SUBSYSTEM ..............................................................................3-2
3.2.1 INTEL PENTIUM II PROCESSOR................................................................................3-3
3.2.2 SYSTEM MEMORY...................................................................................................... 3-6
3.2.3 SUBSYSTEM CONFIGURATION.................................................................................3-9

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
iv
CHAPTER 4 SYSTEM SUPPORT....................................................................................................4-1
4.1 INTRODUCTION.................................................................................................................. 4-1
4.2 PCI BUS OVERVIEW...........................................................................................................4-2
4.2.1 PCI CONNECTOR.........................................................................................................4-3
4.2.2 PCI BUS MASTER ARBITRATION..............................................................................4-4
4.2.3 PCI BUS TRANSACTIONS...........................................................................................4-5
4.2.4 OPTION ROM MAPPING .............................................................................................4-8
4.2.5 PCI INTERRUPT MAPPING.........................................................................................4-9
4.2.6 PCI POWER MANAGEMENT SUPPORT.....................................................................4-9
4.2.7 PCI CONFIGURATION............................................................................................... 4-10
4.3 AGP BUS OVERVIEW .......................................................................................................4-11
4.3.1 BUS TRANSACTIONS................................................................................................4-11
4.3.2 AGP CONFIGURATION............................................................................................. 4-14
4.4 ISA BUS OVERVIEW......................................................................................................... 4-15
4.4.1 ISA CONNECTOR ......................................................................................................4-16
4.4.2 ISA BUS TRANSACTIONS......................................................................................... 4-17
4.4.3 DIRECT MEMORY ACCESS......................................................................................4-19
4.4.4 INTERRUPTS.............................................................................................................. 4-22
4.4.5 INTERVAL TIMER..................................................................................................... 4-26
4.4.6 ISA CONFIGURATION...............................................................................................4-26
4.5 SYSTEM CLOCK DISTRIBUTION.................................................................................... 4-27
4.6 REAL-TIME CLOCK AND CONFIGURATION MEMORY............................................... 4-28
4.7 I/O MAP AND REGISTER ACCESSING............................................................................ 4-45
4.7.1 SYSTEM I/O MAP ......................................................................................................4-45
4.7.2 GPIO UTILIZATION................................................................................................... 4-46
4.8 SYSTEM MANAGEMENT SUPPORT ............................................................................... 4-50
4.8.1 FLASH ROM WRITE PROTECT ................................................................................4-51
4.8.2 PASSWORD PROTECTION........................................................................................ 4-51
4.8.3 I/O SECURITY............................................................................................................ 4-52
4.8.4 USER SECURITY........................................................................................................4-52
4.8.5 TEMPERATURE SENSING........................................................................................4-53
4.8.6 SMART COVER LOCK...............................................................................................4-54
4.8.7 BACKPLANE DETECT ..............................................................................................4-54
4.8.8 POWER MANAGEMENT........................................................................................... 4-55
CHAPTER 5 INPUT/OUTPUT INTERFACES................................................................................5-1
5.1 INTRODUCTION.................................................................................................................. 5-1
5.2 ENHANCED IDE INTERFACE............................................................................................ 5-1
5.2.1 IDE PROGRAMMING...................................................................................................5-1
5.2.2 IDE CONNECTOR........................................................................................................5-8
5.3 DISKETTE DRIVE INTERFACE..........................................................................................5-9
5.3.1 DISKETTE DRIVE PROGRAMMING ........................................................................ 5-10
5.3.2 DISKETTE DRIVE CONNECTOR.............................................................................. 5-13
5.4 SERIAL INTERFACES....................................................................................................... 5-14
5.4.1 RS-232 INTERFACE ................................................................................................... 5-14
5.4.2 SERIAL INTERFACE PROGRAMMING.................................................................... 5-15

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
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5.5 PARALLEL INTERFACE................................................................................................... 5-20
5.5.1 STANDARD PARALLEL PORT MODE ..................................................................... 5-20
5.5.2 ENHANCED PARALLEL PORT MODE..................................................................... 5-21
5.5.3 EXTENDED CAPABILITIES PORT MODE............................................................... 5-21
5.5.4 PARALLEL INTERFACE PROGRAMMING.............................................................. 5-22
5.5.5 PARALLEL INTERFACE CONNECTOR ................................................................... 5-26
5.6 KEYBOARD/POINTING DEVICE INTERFACE ............................................................... 5-27
5.6.1 KEYBOARD INTERFACE OPERATION ...................................................................5-27
5.6.2 POINTING DEVICE INTERFACE OPERATION .......................................................5-29
5.6.3 KEYBOARD/POINTING DEVICE INTERFACE PROGRAMMING ......................... 5-29
5.6.4 KEYBOARD/POINTING DEVICE INTERFACE CONNECTOR................................ 5-33
5.7 UNIVERSAL SERIAL BUS INTERFACE...........................................................................5-34
5.7.1 USB KEYBOARD CONSIDERATIONS...................................................................... 5-34
5.7.2 USB CONFIGURATION.............................................................................................. 5-34
5.7.3 USB CONTROL........................................................................................................... 5-35
5.7.4 USB CONNECTOR .....................................................................................................5-35
5.8 AUDIO SUBSYSTEM.........................................................................................................5-36
5.8.1 PCM AUDIO PROCESSING........................................................................................ 5-38
5.8.2 FM SYNTHESIS AUDIO PROCESSING..................................................................... 5-40
5.8.3 PROGRAMMING........................................................................................................ 5-41
5.8.3 SPECIFICATIONS.......................................................................................................5-44
5.9 NETWORK INTERFACE CONTROLLER..........................................................................5-45
5.10.1 FUNCTIONAL DESCRIPTION................................................................................... 5-45
5.10.2 POWER MANAGEMENT SUPPORT.......................................................................... 5-46
5.10.3 CONFIGURATION/CONTROL................................................................................... 5-47
5.10.4 RJ-45 CONNECTOR....................................................................................................5-47
5.10.5 SPECIFICATIONS.......................................................................................................5-47
CHAPTER 6 GRAPHICS SUBSYSTEM..........................................................................................6-1
6.1 INTRODUCTION.................................................................................................................. 6-1
6.2 FUNCTIONAL DESCRIPTION.............................................................................................6-2
6.2.1 ATI RAGE PRO TURBO AGP GRAPHICS CONTROLLER.........................................6-3
6.3 DISPLAY MODES................................................................................................................ 6-4
6.4 PROGRAMMING..................................................................................................................6-5
6.4.1 CONFIGURATION........................................................................................................6-5
6.4.2 CONTROL..................................................................................................................... 6-5
6.5 MONITOR POWER MANAGEMENT CONTROL...............................................................6-6
6.6 CONNECTORS.....................................................................................................................6-6
6.6.1 MEMORY EXPANSION CONNECTOR....................................................................... 6-6
6.6.2 MONITOR CONNECTOR.............................................................................................6-7

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
vi
CHAPTER 7 POWER SUPPLY AND DISTRIBUTION..................................................................7-1
7.1 INTRODUCTION.................................................................................................................. 7-1
7.2 POWER SUPPLY ASSEMBLY/CONTROL..........................................................................7-1
7.2.1 POWER SUPPLY ASSEMBLY.....................................................................................7-2
7.2.2 POWER CONTROL....................................................................................................... 7-3
7.3 POWER DISTRIBUTION......................................................................................................7-5
7.3.1 3.3/5/12 VDC DISTRIBUTION......................................................................................7-5
7.3.2 LOW VOLTAGE DISTRIBUTION................................................................................7-6
7.4 SIGNAL DISTRIBUTION.....................................................................................................7-7
CHAPTER 8 BIOS ROM ..................................................................................................................8-1
8.1 INTRODUCTION.................................................................................................................. 8-1
8.2 BOOT/RESET FUNCTIONS.................................................................................................8-2
8.2.1 BOOT BLOCK...............................................................................................................8-2
8.2.2 QUICKBOOT.................................................................................................................8-2
8.2.3 SILENTBOOT ............................................................................................................... 8-2
8.2.4 RESET...........................................................................................................................8-2
8.3 MEMORY DETECTION AND CONFIGURATION..............................................................8-3
8.4 DESKTOP MANAGEMENT SUPPORT ...............................................................................8-4
8.4.1 SYSTEM ID................................................................................................................... 8-6
8.4.2 SYSTEM INFORMATION TABLE...............................................................................8-6
8.4.3 EDID RETRIEVE ........................................................................................................ 8-13
8.4.4 DRIVE FAULT PREDICTION.....................................................................................8-13
8.4.5 SYSTEM MAP RETRIEVAL....................................................................................... 8-14
8.4.6 FLASH ROM FUNCTIONS......................................................................................... 8-15
8.4.7 POWER BUTTON FUNCTIONS................................................................................. 8-15
8.4.8 ACCESSING CMOS.................................................................................................... 8-16
8.4.9 ACCESSING CMOS FEATURE BITS......................................................................... 8-16
8.4.10 SECURITY FUNCTIONS............................................................................................ 8-18
8.5 PNP SUPPORT.................................................................................................................... 8-19
8.5.1 SMBIOS....................................................................................................................... 8-20
8.6 POWER MANAGEMENT FUNCTIONS ............................................................................ 8-21
8.6.1 INDEPENDENT PM SUPPORT .................................................................................. 8-21
8.6.2 ACPI SUPPORT...........................................................................................................8-21
8.6.3 APM SUPPORT........................................................................................................... 8-22
8.7 USB LEGACY SUPPORT ...................................................................................................8-24
8.8 BIOS UPGRADING............................................................................................................. 8-24
APPENDIX A ERROR MESSAGES AND CODES......................................................................... A-1
A.1 INTRODUCTION.................................................................................................................A-1
A.2 POWER-ON MESSAGES..................................................................................................... A-1
A.3 BEEP/KEYBOARD LED CODES........................................................................................ A-1
A.4 POWER-ON SELF TEST (POST) MESSAGES.................................................................... A-2
A.5 PROCESSOR ERROR MESSAGES (1XX-XX) ...................................................................... A-3
A.6 MEMORY ERROR MESSAGES (2XX-XX)........................................................................... A-4
A.7 KEYBOARD ERROR MESSAGES (30X-XX)....................................................................... A-4
A.8 PRINTER ERROR MESSAGES (4XX-XX)............................................................................ A-5
A.9 VIDEO (GRAPHICS) ERROR MESSAGES (5XX-XX).......................................................... A-5

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
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A.10 DISKETTE DRIVE ERROR MESSAGES (6XX-XX) ......................................................... A-6
A.11 SERIAL INTERFACE ERROR MESSAGES (11XX-XX)................................................... A-6
A.12 MODEM COMMUNICATIONS ERROR MESSAGES (12XX-XX).................................... A-7
A.13 HARD DRIVE ERROR MESSAGES (17XX-XX)............................................................... A-8
A.14 HARD DRIVE ERROR MESSAGES (19XX-XX) ............................................................... A-9
A.15 VIDEO (GRAPHICS) ERROR MESSAGES (24XX-XX) .................................................... A-9
A.16 AUDIO ERROR MESSAGES (3206-XX)......................................................................... A-10
A.17 NETWORK INTERFACE ERROR MESSAGES (60XX-XX) ........................................... A-10
A.18 SCSI INTERFACE ERROR MESSAGES (65XX-XX, 66XX-XX, 67XX-XX) ....................... A-11
A.19 POINTING DEVICE INTERFACE ERROR MESSAGES (8601-XX).............................. A-11
A.20 CEMM PRIVILEDGED OPS ERROR MESSAGES........................................................ A-12
A.21 CEMM EXCEPTION ERROR MESSAGES ................................................................... A-12
APPENDIX B ASCII CHARACTER SET ....................................................................................... B-1
B.1 INTRODUCTION..................................................................................................................B-1
APPENDIX C KEYBOARD............................................................................................................. C-1
C.1 INTRODUCTION..................................................................................................................C-1
C.2 KEYSTROKE PROCESSING................................................................................................C-2
C.2.1 TRANSMISSIONS TO THE SYSTEM ..........................................................................C-3
C.2.2 KEYBOARD LAYOUTS ...............................................................................................C-4
C.2.3 KEYS.............................................................................................................................C-6
C.2.4 KEYBOARD COMMANDS...........................................................................................C-9
C.2.5 SCAN CODES...............................................................................................................C-9

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
viii
LIST OF FIGURES
FIGURE 2–1. COMPAQ DESKPRO EN SERIES SMALL FORM FACTOR PERSONAL COMPUTER WITH MONITOR2-1
FIGURE 2–2. CABINET LAYOUT, FRONT VIEW .......................................................................................2-4
FIGURE 2–3. CABINET LAYOUT, REAR VIEW .........................................................................................2-5
FIGURE 2–4. DESKTOP CHASSIS LAYOUT, TOP VIEW..............................................................................2-6
FIGURE 2–5. BOARD CONNECTOR AND SWITCH LOCATIONS...................................................................2-7
FIGURE 2–6. SYSTEM ARCHITECTURE, BLOCK DIAGRAM........................................................................2-9
FIGURE 2–7. PENTIUM II SEC CARTRIDGE AND HEAT SINK.................................................................. 2-10
FIGURE 3–1. PROCESSOR/MEMORY SUBSYSTEM ARCHITECTURE............................................................ 3-2
FIGURE 3–2. PENTIUM II PROCESSOR INTERNAL ARCHITECTURE............................................................3-3
FIGURE 3–3. SYSTEM MEMORY MAP..................................................................................................... 3-8
FIGURE 4–1. PCI BUS DEVICES AND FUNCTIONS.....................................................................................4-2
FIGURE 4–2. PCI BUS CONNECTOR (32-BIT 5-VOLT TYPE).................................................................... 4-3
FIGURE 4–3. TYPE 0 CONFIGURATION CYCLE........................................................................................ 4-6
FIGURE 4–4. PCI CONFIGURATION SPACE MAP...................................................................................... 4-7
FIGURE 4–5. AGP 1X DATA TRANSFER (PEAK TRANSFER RATE: 266 MB/S)........................................ 4-12
FIGURE 4–6. AGP 2X DATA TRANSFER (PEAK TRANSFER RATE: 532 MB/S)........................................ 4-13
FIGURE 4–7. ISA BUS BLOCK DIAGRAM................................................................................................ 4-15
FIGURE 4–8. ISA EXPANSION CONNECTOR..........................................................................................4-16
FIGURE 4–9. MASKABLE INTERRUPT PROCESSING, BLOCK DIAGRAM.................................................... 4-22
FIGURE 4–10. CONFIGURATION MEMORY MAP.................................................................................... 4-28
FIGURE 5–1. 40-PIN IDE CONNECTOR. .................................................................................................5-8
FIGURE 5–2. 34-PIN DISKETTE DRIVE CONNECTOR.............................................................................. 5-13
FIGURE 5–3. SERIAL INTERFACES BLOCK DIAGRAM ............................................................................. 5-14
FIGURE 5–4. SERIAL INTERFACE CONNECTOR (MALE DB-9 AS VIEWED FROM REAR OF CHASSIS)........... 5-14
FIGURE 5–5. PARALLEL INTERFACE CONNECTOR (FEMALE DB-25 AS VIEWED FROM REAR OF CHASSIS).. 5-26
FIGURE 5–6. 8042-TO-KEYBOARD TRANSMISSION OF CODE EDH, TIMING DIAGRAM............................ 5-27
FIGURE 5–7. KEYBOARD OR POINTING DEVICE INTERFACE CONNECTOR............................................... 5-33
FIGURE 5–8. UNIVERSAL SERIAL BUS CONNECTOR (ONE OF TWO AS VIEWED FROM REAR OF CHASSIS)..... 5-35
FIGURE 5–9. AUDIO SUBSYSTEM BLOCK DIAGRAM .............................................................................. 5-37
FIGURE 5–10. ANALOG SIGNAL SAMPLING/QUANTIZING ...................................................................... 5-38
FIGURE 5–11. DAC OPERATION ......................................................................................................... 5-38
FIGURE 5–12. AUDIO SUBSYSTEM-TO-ISA BUS PCM AUDIO DATA FORMATS / BYTE ORDERING .......... 5-39
FIGURE 5–13. FM SYNTHESIS PATCH.................................................................................................. 5-40
FIGURE 5–14. AUDIO CONTROLLER-TO-ISA BUS FM AUDIO DATA FORMAT ........................................ 5-40
FIGURE 5–15. 10/100 TX NETWORK INTERFACE CONTROLLER BLOCK DIAGRAM ................................. 5-45
FIGURE 5–16. ETHERNET TPE CONNECTOR (RJ-45, VIEWED FROM CARD EDGE) ................................... 5-47
FIGURE 6-1. GRAPHICS SUBSYSTEM BLOCK DIAGRAM ............................................................................6-2
FIGURE 6-2. ATI 3D RAGE PRO TURBO AGP 2X GRAPHICS CONTROLLER ............................................6-3
FIGURE 6-3. VGA MONITOR CONNECTOR............................................................................................. 6-7
FIGURE 7–1. POWER DISTRIBUTION AND CONTROL, BLOCK DIAGRAM....................................................7-1
FIGURE 7–2. POWER CABLE DIAGRAM ..................................................................................................7-5
FIGURE 7–3. LOW VOLTAGE SUPPLY, BLOCK DIAGRAM.........................................................................7-6
FIGURE 7–4. SIGNAL DISTRIBUTION DIAGRAM.......................................................................................7-7
FIGURE 7–5. HEADER PINOUTS .............................................................................................................7-8

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
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FIGURE B–1. ASCII CHARACTER SET ...................................................................................................B-1
FIGURE C–1. KEYSTROKE PROCESSING ELEMENTS, BLOCK DIAGRAM ....................................................C-2
FIGURE C–2. KEYBOARD-TO-SYSTEM TRANSMISSION OF CODE 58H, TIMING DIAGRAM..........................C-3
FIGURE C–3. U.S. ENGLISH (101-KEY) KEYBOARD KEY POSITIONS.......................................................C-4
FIGURE C–4. NATIONAL (102-KEY) KEYBOARD KEY POSITIONS............................................................C-4
FIGURE C–5. U.S. ENGLISH WINDOWS (101W-KEY) KEYBOARD KEY POSITIONS ...................................C-5
FIGURE C–6. NATIONAL WINDOWS (102W-KEY) KEYBOARD KEY POSITIONS ........................................C-5

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
x
LIST OF TABLES
TABLE 1–1. ACRONYMS AND ABBREVIATIONS.......................................................................................1-3
TABLE 2–1. FAMILY DIFFERENCES ..........................................................................................................2-8
TABLE 2–2. SUPPORT CHIPSETS ..........................................................................................................2-11
TABLE 2–3. GRAPHICS SUBSYSTEM OVERVIEW.................................................................................... 2-12
TABLE 2–4. ENVIRONMENTAL SPECIFICATIONS.................................................................................... 2-13
TABLE 2–5. ELECTRICAL SPECIFICATIONS ........................................................................................... 2-13
TABLE 2–6. PHYSICAL SPECIFICATIONS............................................................................................... 2-13
TABLE 2–7. DISKETTE DRIVE SPECIFICATIONS..................................................................................... 2-14
TABLE 2–8. 24X CD-ROM DRIVE SPECIFICATIONS.............................................................................. 2-14
TABLE 2–9. HARD DRIVE SPECIFICATIONS...........................................................................................2-15
TABLE 3–1. PROCESSOR/MEMORY ARCHITECTURAL OVERVIEW...............................................................3-1
TABLE 3–2. BUS/CORE SPEED SWITCH SETTINGS...................................................................................3-5
TABLE 3–3. SPD ADDRESS MAP (SDRAM DIMM)................................................................................. 3-7
TABLE 3–4. HOST/PCI BRIDGE CONFIGURATION REGISTERS (443BX, FUNCTION 0) ................................3-9
TABLE 4–1. PCI BUS CONNECTOR PINOUT............................................................................................4-3
TABLE 4–2. PCI BUS MASTERING DEVICES...........................................................................................4-4
TABLE 4–3. PCI DEVICE CONFIGURATION ACCESS................................................................................4-6
TABLE 4–4. PCI FUNCTION CONFIGURATION ACCES..............................................................................4-7
TABLE 4–5. PCI DEVICE IDENTIFICATION ............................................................................................. 4-8
TABLE 4–6. PCI/ISA BRIDGE CONFIGURATION REGISTERS (82371, FUNCTION 0).................................. 4-10
TABLE 4–7. PCI/AGP BRIDGE CONFIGURATION REGISTERS (82371, FUNCTION 1)................................. 4-14
TABLE 4–8. ISA EXPANSION CONNECTOR PINOUT............................................................................... 4-16
TABLE 4–9. DEFAULT DMA CHANNEL ASSIGNMENTS ......................................................................... 4-19
TABLE 4–10. DMA PAGE REGISTER ADDRESSES................................................................................. 4-20
TABLE 4–11. DMA CONTROLLER REGISTERS...................................................................................... 4-21
TABLE 4–12. MASKABLE INTERRUPT PRIORITIES AND ASSIGNMENTS.................................................... 4-23
TABLE 4–13. MASKABLE INTERRUPT CONTROL REGISTERS.................................................................. 4-23
TABLE 4–14. INTERVAL TIMER FUNCTIONS .........................................................................................4-26
TABLE 4–15. INTERVAL TIMER CONTROL REGISTERS........................................................................... 4-26
TABLE 4–16. CLOCK GENERATION AND DISTRIBUTION ........................................................................ 4-27
TABLE 4–17. CONFIGURATION MEMORY (CMOS) MAP....................................................................... 4-29
TABLE 4–18. SYSTEM I/O MAP........................................................................................................... 4-45
TABLE 4–19. 82371 SOUTH BRIDGE GENERAL PURPOSE INPUT PORT UTILIZATION ............................... 4-46
TABLE 4–20. 82371 SOUTH BRIDGE GENERAL PURPOSE OUTPUT PORT UTILIZATION............................ 4-47
TABLE 4–21. 87307 I/O CONTROLLER PNPSTANDARD CONTROL REGISTERS......................................... 4-48
TABLE 4–22. SYSTEM MANAGEMENT CONTROL REGISTERS................................................................... 4-50
TABLE 5–1. IDE PCI CONFIGURATION REGISTERS ................................................................................ 5-2
TABLE 5–2. IDE BUS MASTER CONTROL REGISTERS ............................................................................. 5-2
TABLE 5–3. IDE ATA CONTROL REGISTERS.........................................................................................5-3
TABLE 5–4. IDE CONTROLLER COMMANDS ..........................................................................................5-6
TABLE 5–5. 40-PIN IDE CONNECTOR PINOUT .......................................................................................5-8
TABLE 5–6. DISKETTE DRIVE CONTROLLER CONFIGURATION REGISTERS ............................................. 5-10
TABLE 5–7. DISKETTE DRIVE CONTROLLER REGISTERS ....................................................................... 5-11
TABLE 5–8. 34-PIN DISKETTE DRIVE CONNECTOR PINOUT................................................................... 5-13
TABLE 5–9. DB-9 SERIAL CONNECTOR PINOUT................................................................................... 5-14

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
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TABLE 5–10. SERIAL INTERFACE CONFIGURATION REGISTERS.............................................................. 5-15
TABLE 5–11. SERIAL INTERFACE CONTROL REGISTERS........................................................................ 5-16
TABLE 5–12. PARALLEL INTERFACE CONFIGURATION REGISTERS......................................................... 5-22
TABLE 5–13. PARALLEL INTERFACE CONTROL REGISTERS ................................................................... 5-23
TABLE 5–14. DB-25 PARALLEL CONNECTOR PINOUT .......................................................................... 5-26
TABLE 5–15. 8042-TO-KEYBOARD COMMANDS .................................................................................. 5-28
TABLE 5–16. KEYBOARD/MOUSE INTERFACE CONFIGURATION REGISTERS ........................................... 5-29
TABLE 5–17. CPU COMMANDS TO THE 8042...................................................................................... 5-31
TABLE 5–18. KEYBOARD/POINTING DEVICE CONNECTOR PINOUT........................................................ 5-33
TABLE 5–19. USB INTERFACE CONFIGURATION REGISTERS................................................................. 5-34
TABLE 5–20. USB CONTROL REGISTERS............................................................................................. 5-35
TABLE 5–21. USB CONNECTOR PINOUT.............................................................................................. 5-35
TABLE 5–22. AUDIO MODE DIFFERENCES............................................................................................ 5-39
TABLE 5–23. AUDIO SUBSYSTEM I/O MAP ..........................................................................................5-42
TABLE 5–24. COMPATIBILITY MODE AUDIO MIXER CONTROL REGISTER MAPPING ............................... 5-42
TABLE 5–25. EXTENDED MODE AUDIO MIXER CONTROL REGISTER MAPPING ...................................... 5-43
TABLE 5–26. FM SYNTHESIZER CONTROL REGISTER MAPPING ............................................................ 5-43
TABLE 5–27. AUDIO SUBSYSTEM SPECIFICATIONS ............................................................................... 5-44
TABLE 5–28. OPERATING SPECIFICATIONS...........................................................................................5-47
TABLE 6–1. 2D GRAPHICS DISPLAY MODES (W/SGRAM)......................................................................6-4
TABLE 6–1. 3D GRAPHICS DISPLAY MODES ..........................................................................................6-4
TABLE 6–1. ATI RAGE PRO PCI CONFIGURATION SPACE REGISTERS ..................................................6-5
TABLE 6–1. STANDARD VGA MODE I/O MAPPING................................................................................6-5
TABLE 6–1. MONITOR POWER MANAGEMENT CONDITIONS....................................................................6-6
TABLE 6–1. DB-15 MONITOR CONNECTOR PINOUT............................................................................... 6-7
TABLE 7–1. POWER SUPPLY ASSEMBLY SPECIFICATIONS........................................................................7-2
TABLE 8–1. DESKTOP MANAGEMENT FUNCTIONS (INT15) ....................................................................8-4
TABLE 8–1. PNP BIOS FUNCTIONS..................................................................................................... 8-19
TABLE 8–2. APM BIOS FUNCTIONS (INT15) .....................................................................................8-23
TABLE A–1. POWER-ON MESSAGES ..................................................................................................... A-1
TABLE A–2. BEEP/KEYBOARD LED CODES.......................................................................................... A-1
TABLE A–3. POWER-ON SELF TEST (POST) MESSAGES........................................................................ A-2
TABLE A–4. PROCESSOR ERROR MESSAGES ......................................................................................... A-3
TABLE A–5. MEMORY ERROR MESSAGES............................................................................................. A-4
TABLE A–6. KEYBOARD ERROR MESSAGES.......................................................................................... A-4
TABLE A–7. PRINTER ERROR MESSAGES.............................................................................................. A-5
TABLE A–8. VIDEO (GRAPHICS) ERROR MESSAGES .............................................................................. A-5
TABLE A–9. DISKETTE DRIVE ERROR MESSAGES.................................................................................. A-6
TABLE A–10. SERIAL INTERFACE ERROR MESSAGES............................................................................. A-6
TABLE A–11. SERIAL INTERFACE ERROR MESSAGES............................................................................. A-7
TABLE A–12. HARD DRIVE ERROR MESSAGES...................................................................................... A-8
TABLE A–13. HARD DRIVE ERROR MESSAGES...................................................................................... A-9
TABLE A–14. HARD DRIVE MESSAGES................................................................................................. A-9
TABLE A–15. AUDIO ERROR MESSAGES............................................................................................. A-10
TABLE A–16. NETWORK INTERFACE ERROR MESSAGES...................................................................... A-10
TABLE A–17. SCSI INTERFACE ERROR MESSAGES ............................................................................. A-11
TABLE A–18. POINTING DEVICE INTERFACE ERROR MESSAGES........................................................... A-11
TABLE A–19. CEMM PRIVILEGED OPS ERROR MESSAGES.................................................................. A-12
TABLE A–20. CEMM EXCEPTION ERROR MESSAGES ......................................................................... A-12

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
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TABLE C–1. KEYBOARD-TO-SYSTEM COMMANDS .................................................................................C-9
TABLE C–2. KEYBOARD SCAN CODES.................................................................................................C-10

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
1-1
Chapter 1
INTRODUCTION
1. Chapter 1 INTRODUCTION
1.1 ABOUT THIS GUIDE
This guide provides technical information about the Compaq Deskpro EN Series of Net PC and
Small Form Factor Personal Computers. This document includes information regarding system
design, function, and features that can be used by programmers, engineers, technicians, and
system administrators.
1.1.1 USING THIS GUIDE
This guide consists of chapters and appendices. The chapters primarily describe the hardware
and firmware elements contained within the chassis and specifically deal with the system board
and the power supply assembly. The appendices contain general information about standard
peripheral devices such as the keyboard as well as separate audio or other interface cards, as well
as other general information in tabular format.
1.1.2 ADDITIONAL INFORMATION SOURCES
This guide does not describe in detail other manufacturer’s components used in the product
covered. For more information on individual commercial-off-the-shelf (COTS) components refer
to the indicated manufacturers’ documentation. The products covered by this guide use
architecture based on industry-standard specifications that can be referenced for detailed
information.
Hardcopy documentation sources:
♦The Lotus/Intel/Microsoft Expanded Memory Specification, Ver. 4.0
♦PCI Local Bus Specification Revision 2.1
Online information sources:
♦Compaq Computer Corporation: http://www.compaq.com
♦Intel Corporation: http://www.intel.com
♦National Semiconductor Incorporated: http://www.national.com
♦ATI Incorporated: http://www.atitech.com

Chapter 1 Introduction
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition – June 1998
1-2
1.2 NOTATIONAL CONVENTIONS
1.2.1 VALUES
Hexadecimal values are indicated by the letter “h” following an alpha-numerical value. Binary
values are indicated by the letter “b” following a value of ones and zeros. Memory addresses
expressed as “SSSS:OOOO” (SSSS = 16-bit segment, OOOO = 16-bit offset) can be assumed as
a hexadecimal value. Values that have no succeeding letter can be assumed to be decimal.
1.2.2 RANGES
Ranges or limits for a parameter are shown as a pair of values separated by two dots:
Example: Bits <7..4> = bits 7, 6, 5, and 4.
1.2.3 SIGNAL LABELS
Signal names are indicated using abbreviations, acronyms, or, if possible, the full signal name in
all capital letters. Signals that are meant to be active low are indicated with a dash immediately
following the name.
1.2.4 REGISTER NOTATION AND USAGE
This guide uses standard Intel naming conventions in discussing the microprocessor’s (CPU)
internal registers. Registers that are accessed through programmable I/O using an indexing
scheme are indicated using the following format:
03C5.17h
Index port
Data port
In the example above, register 03C5.17h is accessed by writing the index port value 17h to the
index address (03C4h), followed by a write to or a read from port 03C5h.
1.2.5 BIT NOTATION
Bit values are labeled with bit <0> representing the least-significant bit (LSb) and bit <7>
representing the most-significant bit (MSb) of a byte. Bytes, words, double words, and quad
words are typically shown with most-significant portions on the left or top and the least-
significant portions on the right or bottom respectively.

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
1-3
1.3 COMMON ACRONYMS AND ABBREVIATIONS
Table 1-1 lists the acronyms and abbreviations used in this guide.
Table 1–1. Acronyms and Abbreviations
Table 1-1.
Acronyms and Abbreviations
Acronym/Abbreviation Description
A ampere
AC alternating current
ACPI Advanced Configuration and Power Interface
A/D analog-to-digital
AGP Accelerated graphics port
API application programming interface
APM advanced power management
ASIC application-specific integrated circuit
AT 1. attention (commands) 2. 286-based PC architecture
ATA AT attachment (mode)
AVI audio-video interleaved
AVGA Advanced VGA
BCD binary-coded decimal
BIOS basic input/output system
bis second/new revision
BitBLT bit block transfer
BNC Bayonet Neill-Concelman (connector)
bps or b/s bits per second
BSP Bootstrap processor
BTO Built to order
CAS column address strobe
CD compact disk
CD-ROM compact disk read-only memory
CDS compact disk system
CF carry flag
CGA color graphics adapter
Ch channel
CLUT color look-up table (pallete)
cm centimeter
CMC cache/memory controller
CMOS complimentary metal-oxide semiconductor (configuration memory)
Cntlr controller
Cntrl control
codec compressor/decompressor
CPQ Compaq
CPU central processing unit
CRT cathode ray tube
CSM Compaq system management / Compaq server management
CTO Configure to order
DAA direct access arrangement
DAC digital-to-analog converter
db decibel
DC direct current
DCH DOS compatibility hole
DDC Display Data Channel
DF direction flag
Continued

Chapter 1 Introduction
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition – June 1998
1-4
Table 1-1. Acronyms and Abbreviations
Continued
Acronym/Abbreviation Description
DIMM dual inline memory module
DIN Deutche IndustriNorm (connector standard)
DIP dual inline package
DMA direct memory access
DMI Desktop management interface
dpi dots per inch
DRAM dynamic random access memory
DRQ data request
EDID extended display identification data
EDO extended data out (RAM type)
EEPROM electrically eraseable PROM
EGA enhanced graphics adapter
EIA Electronic Industry Association
EISA extended ISA
EPP enhanced parallel port
EIDE enhanced IDE
ESCD Extended System Configuration Data (format)
EV Environmental Variable (data)
ExCA Exchangeable Card Architecture
FIFO first in / first out
FL flag (register)
FM frequency modulation
FPM fast page mode (RAM type)
FPU Floating point unit (numeric or math coprocessor)
ft foot
GB gigabyte
GND ground
GPIO general purpose I/O
GPOC general purpose open-collector
GART Graphics address re-mapping table
GUI graphics user interface
h hexadecimal
HW hardware
hex hexadecimal
Hz hertz
IDE integrated drive element
IEEE Institute of Electrical and Electronic Engineers
IF interrupt flag
I/F interface
in inch
INT interrupt
I/O input/output
IPL initial program loader
IrDA InfraRed Data Association
IRQ interrupt request
ISA industry standard architecture
JEDEC Joint Electron Device Engineering Council
Kb / KB kilobits / kilobytes (x 1024 bits / x 1024 bytes)
Kb/s kilobits per second
kg kilogram
KHz kilohertz
kv kilovolt
Continued

Technical Reference Guide
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition - June 1998
1-5
Table 1-1. Acronyms and Abbreviations
Continued
Acronym/Abbreviation Description
lb pound
LAN local area network
LCD liquid crystal display
LED light-emitting diode
LIF low insertion force (socket)
LSI large scale integration
LSb / LSB least significant bit / least significant byte
LUN logical unit (SCSI)
MMX multimedia extensions
MPEG Motion Picture Experts Group
ms millisecond
MSb / MSB most significant bit / most significant byte
mux multiplex
MVA motion video acceleration
MVW motion video window
n variable parameter/value
NIC network interface card/controller
NiCad nickel cadmium
NiMH nickel-metal hydride
NMI non-maskable interrupt
ns nanosecond
NT nested task flag
NTSC National Television Standards Committee
NVRAM non-volatile random access memory
OEM original equipment manufacturer
OS operating system
PAL 1. programmable array logic 2. phase altering line
PC personal computer
PCI peripheral component interconnect
PCM pulse code modulation
PCMCIA Personal Computer Memory Card International Association
PF parity flag
PIN personal identification number
PIO Programmed I/O
POST power-on self test
PROM programmable read-only memory
PTR pointer
RAM random access memory
RAS row address strobe
rcvr receiver
RF resume flag
RGB red/green/blue (monitor input)
RH Relative humidity
RMS root mean square
ROM read-only memory
RPM revolutions per minute
RTC real time clock
R/W read/write
Continued

Chapter 1 Introduction
Compaq Deskpro EN Series of Personal Computers
Net PC and Small Form Factor Models
First Edition – June 1998
1-6
Table 1-1. Acronyms and Abbreviations
Continued
Acronym/Abbreviation Description
SCSI small computer system interface
SDRAM Synchronous Dynamic RAM
SEC Single Edge-Connector
SECAM sequential colour avec memoire (sequential color with memory)
SF sign flag
SGRAM Synchronous Graphics RAM
SIMM single in-line memory module
SIT system information table
SMART Self Monitor Analysis Report Technology
SMI system management interrupt
SMM system management mode
SMRAM system management RAM
SPD serial presence detect
SPP standard parallel port
SRAM static RAM
STN super twist pneumatic
SVGA super VGA
SW software
TAD telephone answering device
TAM telephone answering machine
TCP tape carrier package
TF trap flag
TFT thin-film transistor
TIA Telecommunications Information Administration
TPE twisted pair ethernet
TPI track per inch
TTl transistor-transistor logic
TV television
TX transmit
UART universal asynchronous receiver/transmitter
UDMA Ultra DMA
us / µs microsecond
USB Universal Serial Bus
UTP unshielded twisted pair
Vvolt
VESA Video Electronic Standards Association
VGA video graphics adapter
vib vibrato
VLSI very large scale integration
VRAM Video RAM
Wwatt
WOL Wake on LAN
WRAM Windows RAM
ZF zero flag
ZIF zero insertion force (socket)