LXE MX1-IS, Справочное руководство

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ROM-DOS Commands 127
E-EQ-MX1ISRG-F MX1 I-Safe Reference Guide
HIMEM.SYS
Installable Device Driver
The HIMEM.SYS device driver manages extended memory and the High Memory Area (HMA)
in a 286, 386 or greater, or PS/2 systems. HIMEM prevents programs from simultaneously using
the same area of memory for two different purposes. HIMEM supports the Extended Memory
Specification (XMS) 2.0. HIMEM is installed as a device driver in CONFIG.SYS.
Syntax
DEVICE = [ d:] [pat h] HIMEM.SYS [/machine:n] [/A20[+]] [/PS2]
[/CONTROLA20:OFF]
Remarks
The HIMEM driver can be used to allow ROM-DOS to run in High Memory.
HIMEM supports a default of 32 handles.
HIMEM should not be used with older versions of Datalight’s VDISK. Current versions of
VDISK use XMS memory if it is available.
HIMEM recognizes PS/2-style A20 line control and determines whether to use the PS/2 A20
control or the AT A20 control method automatically by calling Int 15h, function C0h (get system
configuration). This automatic detection can be overridden with the /Machine:n, /A20, A20+, or
/PS2 command line switches in the event that the auto detection on a given system fails.
/Machine:1 and /A20 both designate the PC AT A20 control method. These switches instruct
HIMEM
not to wait for the A20 line to settle.
/Machine:2 and /PS2 both designate the PS/2 control method.
/A20+ is similar to /A20 but instructs HIMEM to wait for the A20 line to settle.
/Machine:3 designates support for the Phoenix Cascade BIOS A20 control methods.
Alternately, /CONTROLA20:OFF instructs HIMEM to not detect the control method for the A20
line and assumes the A20 line is always on.
The /BIOS switch forces the use of BIOS Int15h, Function 87h, for data transfers to and from
XMS memory.
The /QUIET switch forces HIMEM to remove the sign-on message when loading.
Error Conditions
No Extended Memory— An extended memory error condition can occur if the BIOS (via Int
15H, function 88H) notifies HIMEM that there is no extended memory. In this situation, HIMEM
displays an appropriate error message and does not install.
Failure to Control the A20 Line— When HIMEM installs, it attempts to control the A20 line,
which controls access to the HMA. HIMEM first attempts control via the AT method (using the
8259 keyboard control). If that fails, HIMEM then attempts control via the PS/2 method (using
I/O port 60H). If both methods fail, HIMEM assumes it can’t control the A20 line and displays the
message
A20 Control (OFF)
If either of these errors occur, try using the /A20, /A20+, or /PS2 in the HIMEM command line.