DOS® Beyond 640K 2nd Edition DOS® Beyond 640K 2nd Edition James S. Forney Windcrest®/McGraw-Hill SECOND EDITION FIRST PRINTING © 1992 by James S. Forney. First Edition © 1989 by James S. Forney. Published by Windcrest Books, an imprint of TAB Books. TAB Books is a division of McGraw-Hill, Inc. The name "Windcrest" is a registered trademark of TAB Books. Printed in the United States of America. All rights reserved. The publisher takes no responsibility for the use of any of the materials or methods described in this book, nor for the products thereof. Library of Congress Cataloging-in-Publication Data Forney, James. DOS beyond 640K / by James S. Forney. - 2nd ed. p. cm. Rev. ed. of: MS-DOS beyond 640K. Includes index. ISBN 0-8306-9717-9 ISBN 0-8306-3744-3 (pbk.) 1. Operating systems (Computers) 2. MS-DOS (Computer file) 3. PC -DOS (Computer file) 4. Random access memory. I. Forney, James. MS-DOS beyond 640K. II. Title. QA76.76.063F644 1991 0058.4'3--dc20 91-24629 CIP TAB Books offers software for sale. For information and a catalog, please contact TAB Software Department, Blue Ridge Summit, PA 17294-0850. Acquisitions Editor: Stephen Moore Production: Katherine G. Brown Book Design: Jaclyn J. Boone Cover: Sandra Blair Design, Harrisburg, PA WTl To Sheila Contents Preface Xlll Acknowledgments xv Introduction xvii Chapter 1. The unexpanded system 1 Physical limits of the system 2 The physical machine 5 Life beyond 640K 7 The operating system 10 Evolution: a two-way street 12 What else is in there? 13 Out of hiding 13 Chapter 2. At the heart of things 15 The ubiquitous 8088 16 The 80286 20 The supercharged 80386 23 Above and beyond: the i486 29 An SX version of the i486 30 Boosting performance even more ... sometimes 30 A ticking clock 31 There's more 33 Chapter 3. The new breed 35 A brave new world 35 Games anyone can play 36 The revolution almost no one noticed 40 Meanwhile back at the ranch 41 To the beat of a different drummer 42 And in the center ring . .. 45 Chapter 4. Expanded memory 47 In the beginning 48 A little dinner music, please 48 Using expanded memory 52 Expanded memory that is-but isn't-what it seems 53 Only a stopgap 54 Chapter 5. EMS memory 55 The 4.0 backfill: mapping conventional memory 58 But not for everyone 59 The sheep from the goats 60 Registers: real and fake-and often.missing 60 Bus speed 65 The bottom line 66 Chapter 6. Stealing the store 67 A party of volunteers 70 DOS 5's mMEM.SYS and company 71 Bigger than life 75 Fragmentation 76 Declaring open season on the BIOS 78 For want of a map 79 It went where? 81 Stealing still another 64K-maybe even 96K 81 Don't count the 80286 out yet 83 Chapter 7. Extended memory and new frontiers 85 A quick review 86 Protected mode 87 Bottoms up 89 Enter the DOS extender 90 Lotus put it all together-just like 1-2-3 92 Canned answers for uncanny problems 95 What's a VCPI? 98 DPMI: a light in the window 99 In these muddy waters 100 Chapter 8. DOS's mysterious "extra" 64K 103 With a little sleight of hand 104 Fool's gold 107 Gift or Trojan horse? 108 Digging for gold the old-fashioned way 109 Chapter 9. Chairmen of the board 113 The changing face of management 113 Duos, quartets, and one-man bands 114 New directions 115 Getting down to brass tacks 117 Super specialists 118 Gentlemen, start your engines 119 Me too 121 Exceptions to the rule 122 Shots in the dark 123 Getting downright pushy 123 Chapter 10. Two times 5.0 127 Left foot, right foot 128 The Microsoft connection 128 A cut above 130 Just having EMS is not enough 130 From digital research: DR DOS 5.0 134 More than just a matter of semantics 135 Configuring your system on the fly 137 Choices, choices 138 Don't send a boy to do a man's work 139 Chapter 11. Entry-level answers 141 More room with HeadRoom 142 Context switching: Carousel's revolving door approach 145 Task swapping under the DOSs 146 Task switching lurking in the background 148 FAX boards 148 Spoolers and buffered output 149 Peripheral sharing 151 It all helps-but is it enough? 151 Chapter 12. DESQview and the age of multitasking 153 The heretics 154 A textbook 4.0 EMS case study 156 Stick to the straight and narrow 158 To build a better mousetrap 160 Negative overhead 161 Worlds in collision 163 Windows' windows 164 The tortoise and the hare 164 For power users and beyond 165 DESQview X 166 Chapter 13. Windows 169 About a ton of memory 170 A three-windows world 171 What Windows 3.0 provides, and what it doesn't 172 QEMM 173 386MAX 174 ALL CHARGE 386 176 hDC FirstApps 176 Chapter 14. Beyond the real 179 If it will run on any 8086 machine . .. 180 No virtual clock 181 VM386: multitasking and more 181 A megabyte for everyone 183 A clean environment 185 Split personality 187 Virtual machines do not have virtual crashes 188 More than just one pretty face: the multiuser option 189 Chapter 15. The MOOS multiuser option 191 The virtual machine again 192 Multiuser VM386 193 DR Multiuser DOS 195 The double whammy 196 Idle power 199 PC-MOS 200 Only the tip of the iceberg 204 What you don't see 205 Chapter 16. Keeping up, or trying to 207 Supercharging that old 8088 208 The 286 dilemma 210 The ALL 386SX: a new approach 210 The empire strikes back: Intel's SnapIn 386 211 Charge it with the ALL ChargeCard 212 Adopting a new mother 214 The interleave factor 217 Superfast "disks" and disk caching 219 Chapter 17. The ultimate upgrade 221 Striking a happy medium 222 Cash and carry 224 Down memory lane 225 Ladies-in-waiting 226 Don't miss the bus 226 What's wrong with the old bus? 228 Beyond "advanced technology" 228 Putting the pieces together 231 Recycled oldies 233 No no no! 233 Chapter 18. Crash course 237 The high road 239 Looking in high places-even on an 8088 240 On a higher plane 242 Where did that come from? 243 Any old port in a storm 246 Software crashes can be just as hard 246 Detectives on a disk 249 Chapter 19. Parting shots 253 Ship of fools 254 To stretch a point 254 The more things change 255 The ultimate shell game 256 APPENDICES A. Advanced programming functions available under LIM 4.0 EMS 257 B. Special considerations for mapping LIM 4.0 EMS memory 261 C. Using bootable floppies to test new confIgUrations 265 D. The basics of hexadecimal 269 E. Addresses for the software developers 271 Glossary 273 Index 277 Preface So much has happened since the first edition of this book was published that many of the questions asked then have long since been answered. Someone recently observed that, in the period since the introduction of the mM PC, our use of memory has increased tenfold every five years. We went so quickly from just 64K in those first machines to 640K as the standard in later models. We had reached that tenfold figure less than five years after the introduction of the first PC; however, the 64K figures predates that machine. The five year estimate is pretty close. Another five or so years later, we now have seen another tenfold increase in our needs. To use Windows 3.0 you really need at least 2 Mb; to multitask you'd better add another 2 Mb or 4 Mb more. To do real multitasking effectively in DESQview, VM386, or anyone of several multitaskers, you proba­ bly need at least that much memory. Not only has our appetite for memory become almost insatiable, but-with this appetite, a new genre of hardware, and new, more powerful applications soft­ ware-we must change the way we think about memory and how we access it. Even DOS itself has changed with the introduction of two powerful 5.0 releases from the two key players in the game (old rivals Microsoft and Digital Research), plus a third if you include the new DR Multiuser DOS 5.0, also from Digital. Each DOS addresses the challenge of our exploding needs in its own unique way. Although there is nothing truly novel in the changes any of these three-or any of the severallook-alikes-have made, they do focus attention on the issues in a somewhat different light. In the reflection of that light and the many changes in the issues since this book first was published, we look now not just beyond 640K but to the issues and the answers as we look ahead to DOS's second decade. xiii Acknowledgments Very special thanks once again to Gary Saxer of Quarterdeck Office Systems (Desqview). Without his patience and insights, this project might have fallen short of expectations. Special thanks also to the following (not in order of their contributions): Paul Tarlow at Qualitas, Inc.; John Barrett at All Computers Inc.; Cristy Gersich and Eric Straub at Microsoft; Dirk Smith at Phar Lap; Roger Kasten at Newer Tech­ nology; and Evan Lim at Intelligent Graphics Corporation. Thanks to the following companies that, in addition to those above, still represent only a part ofthe many companies and individuals that generously furnished hard­ ware, software and/or expertise specifically for use in preparing this book and in shaping its direction: ALR ALL Computers Inc.