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Document ID: DJON-3G8RC8

Aptiva - Error Message: Unable to control A20 line

Applicable to: United States

Problem:
HIMEM.SYS did not load properly and therefore cannot make extended memory or the high memory area (HMA) available. If HIMEM.SYS is not loaded correctly, programs such as EMM386.EXE, Windows 3.0, and Windows 3.1x are unable to use extended memory, and Microsoft MS-DOS cannot load into the HMA. This problem occurs if HIMEM.SYS incorrectly identifies your machine type, or if the /CPUCLOCK and /MACHINE switches need to be added to the DEVICE command for HIMEM.SYS.

Solution:
To correct this problem, add the /CPUCLOCK and /MACHINE switches to the DEVICE command that starts HIMEM.SYS:

1. Edit your CONFIG.SYS file. To edit the file using MS-DOS Editor, enter the following at the MS-DOS command prompt:

EDIT C:\CONFIG.SYS

2. Make sure your CONFIG.SYS file contains a DEVICE command for HIMEM.SYS. This command should appear before any other DEVICE commands:

DEVICE=C:\DOS\HIMEM.SYS

3. Add the /CPUCLOCK:ON switch to the DEVICE command for HIMEM.SYS. The command should now appear on one line as follows:

DEVICE=C:\DOS\HIMEM.SYS /CPUCLOCK:ON /V

NOTE: The /V (verbose) switch following the /CPUCLOCK:ON switch forces HIMEM.SYS to display informational messages when it loads.

4. If you're using MS-DOS Editor, choose Exit from the File menu. When MS-DOS Editor displays a dialog box prompting you to save your file, choose the YES button or press ENTER.

5. Restart your computer by pressing CTRL+ALT+DEL. Watch the messages that your computer displays during startup. If HIMEM.SYS is working properly, it should display a message similar to the following:

Installed A20 handler number 1.

64K High Memory Area is available.

If the error message no longer appears, HIMEM.SYS starts correctly, and your system is working properly, the problem has been corrected.

If this did not work, add the /MACHINE switch to it.

Edit your CONFIG.SYS file again. Locate the DEVICE command for HIMEM.SYS and add the /MACHINE switch to it. The /MACHINE switch specifies the type of computer you have. The switch should be followed by a colon (:) and your machine number. For the PS/1 system, choose from the following numbers: 1, 11, 12, or 13.

Example: DEVICE=C:\DOS\HIMEM.SYS /CPUCLOCK:ON /MACHINE:11

(The above should appear on one line.)

If you are using the MS-DOS Editor, choose Exit from the File menu. When MS-DOS Editor displays a dialog box prompting you to save your file, choose YES or press ENTER. Restart your computer by pressing CTRL+ALT+DEL.

	Search Keywords
	Hint Category	DOS/Windows 3.x
	Date Created	17-04-97
	Last Updated	23-03-99
	Revision Date	23-03-2000
	Brand	IBM Aptiva
	Product Family	Aptiva, PS/1
	Machine Type	2011, 2144, 2168, 2121, 2123, 2133, 2155
	Model	C01; C34; M01; NEA; T35; U35; A62; A82; A94; B82; C42; C92; G42; M82; S92; 081; 087; 131; 137; K37; N31; N81; 11E; 13T; 14C; 16E; 17A; 18A; 18T; 19C; 21C; 23C; 28A; 46M; 51D; D50; G11; G13; G43; G46; G46; G49; G49; G50; G53; M40; M40; M46; M46; P11; P13; P43; P50; P53; R04; R05; R06; R09; R38; R42; R43; R44; R84; R86; R87; RO3; S11; S13; S43; S45; S45; S47; S47; S48; S48; S50; S53; W11; W13; W42; W42; W43; W45; W45; W50; W53; 20E; 22T; 24C; 24M; 28V; 39E; 41T; 43C; 45V; 48E; 50T; 52C; 55V; 72E; 74T; 76C; 78C; 79C; 81A; 82E; 84T; 86C; 87C; CC1; D53; G14; G44; G52; G54; G72; G76; G78; G82; NM1; P14; P44; P57; P71; P74; P76; P78; P84; R14; R15; R16; R17; R18; R51; R52; R57; R58; R62; R63; R67; R71; R89; R93; R96; R97; S14; S44; S50; S54; S70; S75; S76; S78; S80; W14; W44; W48; W54; W67; W76; W77; W78; Z33; 28V; 31E; 33T; 37C; 38C; 51E; 54T; 56C; 57C; 88V; BB1; G57; G87; OR1; OR3; OR4; OR5; P89; R28; R29; R31; R74; R78; R82; R98; S55; S85; SR1; US1; W52; W82; 1R2; 66P; 67P; 86P; OR8; 1R1; 1R3; 1R5; 22P; 24P; 25P; 27P; 29P; 63P; 67P; 82P; 83P; OR6; OR7; OR9; 1R0; 1R1; 26P; 62P; 2R0; P30; 2R3; S15
	TypeModel	2144s15
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