DOCUMENT:Q72302 17-DEC-2000 [msdos] TITLE :Specifying A20 Handlers with HIMEM.SYS /M in MS-DOS PRODUCT :Microsoft Disk Operating System PROD/VER:MS-DOS:5.x,6.0,6.2,6.21 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21 ------------------------------------------------------------------------------- SUMMARY ======= MS-DOS version 5.0 includes HIMEM.SYS version 2.77. MS-DOS version 6.0 includes HIMEM.SYS version 3.07. MS-DOS versions 6.2, 6.21, and 6.22 include HIMEM.SYS version 3.10. These versions include an A20 handler for the following computers that can be used with the /M: or /MACHINE switch: CODE Number A20 Handler ---- ------ ----------- at 1 IBM PC/AT ps2 2 IBM PS/2 pt1cascade 3 Phoenix Cascade BIOS hpvectra 4 HP Vectra (A and A+) att6300plus 5 AT&T 6300 Plus acer1100 6 Acer 1100 toshiba 7 Toshiba 1600 and 1200XE wyse 8 Wyse 12.5 MHz 286 tulip 9 Tulip SX zenith 10 Zenith ZBIOS at1 11 IBM PC/AT at2 12 IBM PC/AT (alternative delay) css 12 CSS Labs at3 13 IBM PC/AT (alternative delay) philips 13 Philips fasthp 14 HP Vectra ibm7552 15 IBM 7552 Industrial Computer bullmicral 16 Bull Micral 60 dell 17 Dell XBIOS There are two values that are considered defaults. /M:1 is the standard default for IBM AT-class machines, and t/M:2 is the standard default for IBM PS/2 machines. For most 100-percent-compatible machines, the /M:1, /M:11, /M:12, and /M:13 A-20 handler switches should work. Although the other switches are hardware specific, one may be required for proper operation on certain machines. NOTE: In the above list, the device driver should detect the correct handler to use. The following computers may need the corresponding switch added to the CONFIG.SYS file: System Switch ------ ------ Bull Micral 60 /machine:16 COMPUADD 386 systems /machine:1 or /machine:8 Datamedia 386/486 /machine:2 Hitachi HL500C /machine:8 Intel 301z or 302 /machine:8 JDR 386/33 /machine:1 Toshiba 5100 /machine:7 UNISYS PowerPort /machine:2 MORE INFORMATION ================ The /M switch specifies which hardware the computer is using. If the wrong switch is used, HIMEM.SYS may not load properly or the system may hang. For more information, query on the following words: HIMEM and /M Additional query words: 6.22 5.00 5.00a 6.00 6.20 ====================================================================== Keywords : Technology : kbMSDOSSearch kbMSDOS621 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a Version : MS-DOS:5.x,6.0,6.2,6.21 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2000.