Dec 282017
How to turn your PC into a 80386 machine cheap.
File MOS386.ZIP from The Programmer’s Corner in
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How to turn your PC into a 80386 machine cheap.
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Contents of the PCMOS386.TXT file

Notes on trying out PC-MOS/386 Release 1.01
Steve McMenamin [76530,231]

PC-MOS/386 ("MOS") styles itself as a multi-tasking operating system, designed
expressly for the 80386, that is upward-compatible from DOS. MOS is a product
of The Software Link, Inc. It is available in versions for one, five, and 25
users. I recently checked out the single-user version ($195) on a Compaq Desk
Pro 386 with 4MB RAM. This is a very informal report on my impressions of MOS.

I obtained MOS because I've been searching for a way to make as much RAM as
possible available to a large DBMS application I'm building. The main
constraint is that the DBMS does not exploit expanded memory, so all its RAM
must be contiguous, DOS-visible memory. The best I've done thus far without
resorting to hardware add-ons like Max-It is a 560K Carousel partition under
DOS 3.1 (544K under 3.2). In my evaluation of MOS I was specifically looking
for a way to increase this usable amount, while still retaining the multiple-

patition convenience of Carousel. I mention all this by way of letting you
know that I was _not_ especially interested in MOS's multi-tasking abilities,
or at least not as they relate to concurrent execution. Thus, I made no
special effort to test those abilities.

MOS claims to run DOS programs without modification, and with a few exceptions
I found this to be true. You can install MOS right on top of your DOS hard
disk, simply by using the .MSYS command to initialize the boot record and
then copying in the MOS files. MOS comes up with the next reboot. The file
formats seem interchangable, and many familiar DOS sights are present:
config.sys, autoexec.bat,, and others. MOS commands are _very_
similar in both form and function to DOS commands, though some are slightly
enhanced (for example, there is a built-in command line editor). If you
know DOS, you basically know MOS.

When you boot it up, MOS starts a single task, known as "partition 0", in
the first 640K of RAM. In addition to the usual inhabitants, this base memory
is home to the System Memory Pool (SMP), out of which certain memory is
dynamically allocated for use by device drivers and others. In this version,
it seemed that an SMP of 60K was adequate for up to three partitions.
One of the tech. support reps I spoke with told me that subsequent releases
would require much less SMP memory per task. The the size of the SMP
requirement is important because it limits the usable memory in the base
partition. With an SMP of 60K I was able to use about 500K of the base
partition (these figures are approximate).

When you boot up, partition 0 is the accessed (and only) task.
You create additional partitions (i.e. add concurrent tasks) using the
.ADDTASK command. You specify the amount of memory you wish to make available to the
task, along with other optional information, such as the task's ID number,
the startup batch file, and so forth. Each task is either "accessed" or in
the background, and only one task can be accessed at a time. The accessed
task owns the entire display, so there is no way to keep windows for multiple
tasks on-screen at once a la DesqView. You access a task by typing
ALT-, where N is the task's ID number (e.g. ALT-keypad 1 accesses
task 1. If you find that the ALT- sequence is incompatible with one of
your applications, you can temporarily disable it by typing ALT-999,
which is the toggle sequence for reenabling task switching as well.

Earlier I stated that overhead reduces the usable size of the base partition
to right aroung 500K. I was therefore glad to discover that additional
DOS-compatible partitions can be allocated as large as 630K, of which
all but about 7K (for a copy of COMMAND.COM) is usable by the application.
The few tests I did showed the concurrent processing to be quite smooth,
with very little degredation noticeable when I had three tasks going.

Here's a summary of what worked and what failed: Most of my everyday tools
worked just fine, including PCTools, Norton, SPF/PC, ZIM (a DBMS), Mapmem,
Turbokey, and Memwalk. Several other packages worked to a limited extent.
ProComm seemed to continue to execute disk I/O after displaying the
comm. screen on startup; then it issued a strange error message, but
proceded to function properly. I ran ProComm in multi-tasking mode,
which performs screen I/O via the BIOS, but one of the MOS reps said that
this was not necessary, as MOS would intercept and remap even direct
video I/O from an active background task. I haven't tried this out,
so I cannot verify this claim. ZAPCIS would carry on a CIS session
successfully, but would die -- with MOS complaining about an illegal IRQ
(interrupt vector) -- and hang the machine shortly after the session
ended, but before issuing the "chars per second" stats message.
FilePath _seemed_ to get along with MOS splendidly, but it turned out that
it was only really functional in partition 0. FilePath didn't seem to have
any effect whatever in the upper partitions. The only outright fatality was
Brief (version 1.whatever), which incurred a "General Software Failure"
immediately upon invokation. One of the tech reps said he thought Brief did
some "pseudo-multitasking" of its own, so he was not surprised.

MOS comes with more or less the same additional facilities as does DOS:
an editor (switchable between line and visual modes), DEBUG, print spooler,
RAM disk manager, etc. There are also seemingly extensive facilities for
managing a multi-user system, including provisions for security and
network emulation. I was unable to evaluate these features as I was using
the single-user version. The documentation, on the whole, is well-written.

The vendor's technical support left quite a bit to be desired. The reps
themselves were quite helpful. The difficult part is getting _to_ them.
The Software Link demands that you have both your serial number and your
_invoice_ number on hand, evidently to prove that you purchased MOS from
them directly. Once they are satisfied, you are issued a client number,
which entitles you to a grand total of 30 minutes of telephone assistance.
If you should use your entire allottment, I was told, you would have to
"find a dealer or distributor" who could help. Maybe I've been spoiled by
the high level of customer support provided by Zanthe Information (supplier
of ZIM), but I found the whole MOS tech. support experience infuriating.
You'd think a company trying to secure a niche during the lull before OS/2
would make it a little easier for potential users to become addicted to
their product. I guess not.

Overall, I liked MOS but I can't really use it -- yet. Being able to make
over 600K of contiguous RAM available to an unmodified, non-EMS DOS
application surely does appeal to me. The smooth multi-tasking and clean,
Carousel-like partition switching also impressed me. (Of course, I'd just
finished a _very_ frustrating two weeks with DV 2.0, so perhaps I'm now
more easily pleased.) The only reason I don't switch at least one machine
over to MOS is its failure to support FilePath (or the equivalent) in the
large upper partitions. Once that happens, I'll take another look at MOS.

The next release of MOS is allegedly due in "30 to 60 days". It will
automatically be shipped free of charge to registered owners of Release 1.01.

That's a thumbnail sketch of my first encounter with MOS. If you have any
questions about it please do not hesitate to get in touch with me direclty.

Steve McMenamin

 December 28, 2017  Add comments

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