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

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

ID:CR QEMM-386: Using QEMM-386 with CD-ROM drivers
Quarterdeck Technical Note #261 Filename: CDROM.TEC
by Michael Bolton CompuServe: CDROM.TEC
Last revised: 9/04/92 Category: HW

Subject: Information on running CD-ROM devices and drivers with QEMM-386.


Q. How do I install my CD-ROM to work best with QEMM-386?

In general CD-ROM drives should present no problem for users of QEMM-386. As
with almost all pieces of hardware, however, there are a few details to
consider when installing a new CD-ROM drive or when installing QEMM-386 on a
system which has a CD-ROM already.

Refer to the documentation for your drive and check if it uses addresses
between 640K and 1MB for a ROM or RAM buffer. In most cases QEMM-386 should
be able to detect ROMs and EXCLUDE the addresses in use by them automatically.
RAM buffers are somewhat more difficult for QEMM-386 to detect; these should
be specifically EXCLUDEd on the QEMM386.SYS line in CONFIG.SYS. If your
documentation is unclear on this issue, or if you are having difficulty
determining what addresses your drive is using, try the QEMM Analysis
procedure as described in your QEMM-386 manual, or refer to Quarterdeck
Technical Note #219, "Using QEMM-386's Analysis Procedure" (EXCLUDE.TEC).

Many CD-ROMs are Small Computer System Interface (SCSI) devices and many SCSI
controllers access data through a technique called "bus-mastering". Again,
refer to the documentation that came with your drive. If your controller is
bus-mastering, refer to Quarterdeck Technical Note #121, "Bus-Mastering
Devices and QEMM-386" (BUS-MAST.TEC). Conflicts related to this often result
in a system crash when you access the bus-mastering device; as described in
BUS-MAST.TEC, the best solution is to obtain a VDS driver from the
manufacturer of your controller. If the SCSI device is not being accessed
under Windows Enhanced Mode, the DB=2 parameter on the QEMM386.SYS line in
CONFIG.SYS may provide a workaround to this problem until your SCSI
manufacturer provides a VDS driver. If the SCSI device IS being accessed
under Windows Enhanced Mode, loading SMARTDRV low may provide a temporary
workaround.

Most CD-ROM drives use the Microsoft CD-ROM Extensions to DOS, typically using
a TSR called MSCDEX.EXE to provide these services. MSCDEX takes two
parameters that affect how much memory it uses: "/M:XX" and "/E". The
"/M:XX" parameter (where "XX" is some number) allocates memory for buffering
I/O. Each such buffer uses about 2,067 bytes of conventional memory if loaded
into conventional memory. If you use the "/E" parameter on MSCDEX it will
load these buffers into Expanded memory using about 2,457 bytes of expanded
memory and about 20 bytes of conventional memory per buffer. Users of
QEMM-386 will thus benefit by about 2K per buffer to load their MSCDEX buffers
into Expanded memory.

As of this writing, the OPTIMIZE program which comes with QEMM-386 may fail
to load MSCDEX high. This may be because (with older versions of MSCDEX) the
initialization size of MSCDEX is reported inaccurately during the OPTIMIZE
process. If you have such a problem there are a couple of potential
workarounds. The first is to acquire the latest version of MSCDEX from the
manufacturer of your CD-ROM. Another may be to reduce the initialization size
of MSCDEX; you can do this by adding the /M:4 parameter to the MSCDEX line in
AUTOEXEC.BAT. Another (which will work if the previous suggestion does not)
is to inform OPTIMIZE that the initialization size of MSCDEX is larger than
OPTIMIZE is led to believe. After the Analysis phase of OPTIMIZE (after the
first re-boot, when you see the screen titled "ANALYSIS COMPLETE"), select O
for Options, then select Option 2, "Modify the Data Collected".

Specify that the initialization size of MSCDEX is 80K, as in the following
example, and continue the OPTIMIZE process; MSCDEX should then load high.
Smaller values may work, especially if you have specified the /M:4 parameter
to MSCDEX.

Program Try to Load Squeeze Initial Final
High? Frame? Temp? Size Size

ADRIVER.SYS Y - - 10698 9975
ANSI.SYS Y - - 6544 2724
BANANA.SYS Y - - 13392 6224
TOMATO.EXE Y - - 29032 21976
MSCDEX.EXE Y - - 23472 16160 <-
MOUSE.COM Y - - 27965 17435 |
ANOTHER.COM Y - - 67854 23127 |
|
|
The values listed above are fairly typical of MSCDEX as of this writing. If
MSCDEX refuses to load high after OPTIMIZE is run, increase these values in 5K
or 10K increments until MSCDEX loads high. Current versions of MSCDEX seem to
do well with 24K initial size and 17K final size; you may wish to try these
values first.

APPENDIX: Obtaining other technotes

Technotes may be obtained from the Quarterdeck BBS (310-314-3227), by
calling QFAX (our automated FAX-back service, at 310-314-3214), on Compuserve
(go QUARTERDECK, library 2), or BIX. Many technotes are also available on
large local BBSs, often in "DESQview" or "multitasking" file areas.

Quarterdeck BBS QFAX# Compuserve BIX
--------------- ----- ---------- ---
BUS-MAST.TEC 121 BUSMAS.TEC Technote names are not changed
EXCLUDE.TEC 219 EXCLUD.TEC for BIX, but may be ZIPped

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* Copyright (C) 1992 by Quarterdeck Office Systems *
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