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5-30 Utility Descriptions
HIMEM
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 = [drive:][path] 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.