Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : QWHITE13.ZIP
Filename : QEXT.TEC

 
Output of file : QEXT.TEC contained in archive : QWHITE13.ZIP

ID:QX QEXT.SYS
Quarterdeck Technical Note #141 Filename: QEXT.TEC
by Stan Young CompuServe: QEXT.TEC
Last revised: 2/12/92 Category: DV

Subject: Documentation for DESQview's XMS driver, QEXT.SYS.


QEXT.SYS is an XMS manager that is compatible with Microsoft's HIMEM.SYS.
QEXT.SYS was written before HIMEM.SYS existed. Its original purpose was to
allow DESQview to load nearly 64K of its code into the HMA, the first 64K of
extended memory, which is the only portion of the extended memory into which a
normal DOS program can be loaded. Quarterdeck discovered the HMA, and
DESQview was the first program to load into the HMA, years before Microsoft
made it possible to put part of the operating system ther with DOS 5. When
the XMS specification was written, Quarterdeck rewrote QEXT.SYS so that it
would provide the same XMS services that HIMEM.SYS does: making the HMA
and extended memory available.

Any user with a 386 and QEMM-386 does not need to load QEXT.SYS: QEMM-386
provides all the same services.

To operate properly, the QEXT.SYS driver must take the first 64K of exTENDed
memory starting at 1 Megabyte. Therefore, it should be loaded as the first
driver in CONFIG.SYS that uses extended memory (before VDISKs and the like).

QEXT.SYS is written to IBM's specification for identifying itself as a VDISK
type utility and therefore devices loaded after it should not overwrite QEXT.
However, if they do, you can expect that DESQview will fail soon after start-
up.

This note only applies to DESQview systems of 2.0 or beyond that are utilizing
the QEXT.SYS driver. QEXT is usable ONLY with 80286 machines that have REAL,
not emulated exTENDed memory. Emulated extended memory (created by utilities
such as AST's REX.SYS or Quarterdeck's EMS2EXT.SYS), cannot be used.

DETERMINING IF QEXT.SYS IS WORKING

QEXT.SYS is working if more memory (approximately 60K) is shown in the "Total
Conventional Memory" cell in Memory Status when it is loaded versus when it is
not loaded. To load QEXT.SYS you must have DEVICE=QEXT.SYS as the first
device using extended memory in your CONFIG.SYS file and you must load
DESQview with the DV.COM loader. If you have an XDV.COM file in your DESQview
directory, rename it to DV.COM.

Once loaded, the increased memory should be seen, and the device should not
conflict with any RAM disks, spoolers or any other devices or programs that
use expanded memory. If this is the case, QEXT is working. If not, see
below.

AST SUPERSPOOL AND FASTDISK

Older versions of these extended memory users do not seem to be able to detect
QEXT.SYS. Fortunately, these utilities provide a way to configure as a
parameter the starting address for their memory usage. The syntax for the
parameter is:

/EXTM=a,b

where "a" is the amount of memory to be used and "b" is the starting address.
You may want to consult your AST SuperPak documentation for further
information about this and other possible parameters.

Therefore, if you are using only one of these utilities, "a" would be set to
the amount of memory desired and "b" should be set to 1088, since QEXT starts
at 1024 (1 meg.) and extends for 64K.

If you are using both utilities, to be safe you should calculate the starting
address for Superspool, by adding the memory allocated for FASTDISK to 1088.
Both of these utilities display the starting address of their buffer when they
boot into the system. Check these numbers to be sure neither start at
1000000H.

CONFLICTS WITH RAMDRIVE AND SOME VDISKS

Microsoft produces a VDISK-like utility called RAMDRIVE.SYS that is shipped
with Windows and is included with some versions of MS-DOS. Old versions of
this utility do not follow the IBM DOS specification for identifying
installed VDISKs and are not compatible with QEXT.SYS.

There have been isolated cases of MS-DOS versions of VDISK.SYS that also do
not seem to detect QEXT.SYS. If this seems to be a problem, you might contact
the manufacturer of your hardware, or try running IBM DOS and VDISK on your
machine.

INCOMPATIBILITY WITH SOME "COMPATIBLES"

As noted, QEXT.SYS must be very particular about the kind of memory it loads
into and the location. It has been know to fail to load on some compatibles
where the memory starting at 1 Meg. does not look exactly like IBM extended
memory. If you have extended memory and QEXT.SYS fails to load when specified
as THE ONLY driver in the CONFIG.SYS file, and booted with no AUTOEXEC.BAT
file, you may assume you have a hardware incompatibility in extended memory
and should contact the manufacturer of the machine. This has not been a
common problem.

************************************************************************
*This technical note may be copied and distributed freely as long as it*
*is distributed in its entirety and it is not distributed for profit. *
* Copyright (C) 1988-92 by Quarterdeck Office Systems *
************************ E N D O F F I L E *************************