ID:LH LOADHI.SYS and LOADHI.COM
Quarterdeck Technical Note #138
by Joe Wilder

This Technical Note was written before QEMM 5.0 was released.  QEMM
5 has new features such as OPTIMIZE that make this information less
necessary. OPTIMIZE will LOADHI TSR's and Device Drivers in the
most "Optimal" way, sometimes testing millions of different
scenarios.  In addition, the new LOADHI programs are more powerful
than the old, have new parameters for determining the size of a
particular TSR or Device Driver, and can locate these items in
"High Memory" with greater specificity.  Nevertheless, the
information that follows can certainly be of use in helping to
understand QEMM's LOADHI systems.

The LOADHI programs are used to run resident programs and drivers
in the memory area between 640K and 1024K.  This area is normally
reserved for hardware devices such as video cards, system ROM and
Network Adapters.  The more devices you have, i.e. the more
reserved memory you have used, the less there will be available for
using LOADHI to load programs.

LOADHI comes in two forms: 

1-LOADHI.COM is used to load resident programs high in the
AUTOEXEC.BAT or from the DOS prompt. For example to load MOUSE.COM
high you would enter "LOADHI MOUSE.COM" from the DOS prompt or in
the AUTOEXEC.BAT.  

2-LOADHI.SYS is used to load programs high from the CONFIG.SYS. 
For example to load ANSI.SYS high you would put a line in the
CONFIG.SYS that says "DEVICE=LOADHI.SYS ANSI.SYS".

Many new DESQview users assume that LOADHI can load TSR's and
device drivers into extended or expanded memory.  This is not the 
case.  The only place these programs can be loaded is in free and 
contiguous areas in the memory area from 640K to 1024K.  Since a
64K page frame also must be installed somewhere in this area, the 
available reserved is usually fragmented into several segments.

All programs must be loaded into contiguous memory.  Because of
this, you will probably have more luck loading smaller TSR's than
large ones.  This varies from computer to computer and also depends
on the devices installed on the particular computer.  The LOADHI
program always uses the largest area available first.  For network
drivers this may not be desirable.  For instance,  Novell, which
uses two programs, likes to have its smaller program loaded first. 
To load the smaller program first into the smaller of two areas use
LOADHI redundantly.  Example; "LOADHI LOADHI IPX".  The first copy
of LOADHI loads another copy of LOADHI into the first (and larger)
memory area available.  The second copy of LOADHI then loads IPX
into the next largest area available.  Each time LOADHI gets used
it erases itself from memory.  At this point IPX is loaded into the
smaller of the two areas.  The larger is now again fully available. 
Using a single LOADHI to load NET3 (the second and the larger of
the Novell programs) will put it in the larger memory area.  Typing
LOADHI at the DOS prompt reveals areas available for loading high.

The RAM parameter to QEMM.SYS must be invoked in order to use
LOADHI programs. This attaches some expanded memory to the unused
addresses in the reserved memory area.  Once the RAM is available,
programs can be loaded there with LOADHI.  Using the RAM parameter
to QEMM.SYS prevents QEMM from being turned off.  

When using QEMM386 with DESQview there is one other thing to
consider.  DESQview has the capability of running most of its own
code in the reserved memory area.  You don't have to use the RAM
parameter with QEMM to get this feature.   XDV will map expanded
memory onto the available addresses all by itself.  It will then
run DESQview in that memory. 

DESQview can use as much as 140K of reserved memory. Loading high
too many resident programs and drivers before going into DESQview
may cause DESQview to load more of itself into the lower 640K,
resulting in no gain for the largest available window size in
DESQview.  If you are running DESQview, it is therefore a good idea
to avoid loading "Pop-up" type TSR's before DESQview at all (using
LOADHI or not) and install them instead in DESQview windows, where
their overhead to lower memory can be completely overcome.

        Copyright (C) 1991 by Quarterdeck Office Systems
             * * *   E N D   O F   F I L E    * * *