DOS Tasks under Unix: Let's hear about it!

Fri May 20 01:29:25 AEST 1988

In article <5090 at ecsvax.UUCP> gas at ecsvax.UUCP (Guerry A. Semones) writes:
>Okay folks, AT&T's 386 based unix for their work group series has
>been available for a short while.  Sun has announced and begun to
>ship their 386i Roadrunner series.  We're starting to see more and
>more 386 based machines running unix with dos as a subtask.  Some
>of us have these machines.  Some of us have only seen the demos.
>And some of us have only Heard about them.
>    How about some of you that have the fortune/misfortune (?) to 
>have this type of setup, let us know what you have been able to do
>with these machines.

There are two major "Dos under Unix" products on the market --
VP/ix from Phoenix (a.k.a Simultask-386 from AT&T, etc.) and 
OS/Merge from Locus.  I am only familiar with the VP/ix based
product from AT&T, and all of my comments below refer to it.

First a  little background -- VP/ix provides  a virtual IBM PC
with floppy drives, a C: and D: hard drive, and the Unix file
system as a NETBIOS network shared drive.  You have a video
adaptor -- either whatever is on your console if you run on the console,
or a Monochrome adaptor card if you run it from a serial port.
Virtual DOS devices can be mapped to unix files/devices via a 
config file.

Note that there is *no* relationship between devices in your
(physical) machine and devices accessable in your (virtual)
DOS emulation. (well ,except for video adaptor on the console).

>    Several questions come to mind.  I've heard bunches about com-
>patibility, ie. will it run lotus, flight simulator, etc?  

Yes, and yes.  The only packages I know of that don't run
are Copywrite and version 1.0 of Enable (later Enable versions
work).  The list of applications tested is over 50 items long.
Pretty much evrybody's favorites (Lotus, Word Perfect, Symphony,
etc.) have been tested and work quite well.  Flight simulator
does run on the console (but not on remote ascii terminals, for
obvious reasons).

>But how
>about that all important question: How fast does the dos subtask
>perform?  

Well, now that gets kinda weird.  You see, some things are faster
(disk i/o is buffered by UNIX, for example), but programs that
count to 10000 to delay 0.5 seconds get very different response
under Simultask386-VP/ix.  Also, if you are running text applications
from a remote ascii terminal, screen updates and keyboard activity
take place at whatever baudrate your terminal runs at, which can
seem awfully slow, esp. dialed up at 2400 baud...

Other wierdness is that the most efficient way to do things under
Simultask386-VP/ix is to use DOS interrupts or BIOS interrupts, whereas
any dyed-in-the wool DOS hacker will tell you you can do serial i/o
faster by hand-coding and directly accessing the UART, similarly for
running the floppy, etc.  Twiddling hardware registers *works* under
VP/ix-Simultask386, but is slower since it must be *emulated*.

>    Has someone tryed putting a large dos application up as a dos 
>subtask to Unix and seeing how well it performs?  Perhaps a massive
>system like PC-SAS, or some other memory-hungry, large database 
>system?

I haven't... 

>    I'd like to know your impressions of how well the dos subtasks
>perform, and what kinds of performance impacts you have seen.

well, as mentioned above, some things are faster, some slower. Unix
scheduling tends to lower priorities on CPU bound tasks, so that with
several users using the machine, the mapping from wall clock time for
a long computation (by computation I mean CPU bound,no i/o, etc.) under
DOS to  VP/ix-Simultask386 goes roughly exponential.  That is, if it 
sits for an hour or two just computing under DOS (with no i/o -- Unix 
bumps your priority back up when you wait for I/O) , it will take a LONG 
TIME under Unix, something that takes under 1 minute on a PC/XT will take 
about the same time under Simultask386-VP/ix.

Programs that do sequential file I/O will be very happy, however,since
the Unix buffer cache pre-fetches sequential reads.

The Norton SI utility gives some extremely impressive numbers for
performance, which are not representative of actual use due mainly
to the small size of the test (it doesn't  run long enough for the
scheduling concerns to become an issue, and its disk i/o all gets
handled by the buffer cache, so it really cooks).

The bottom line is, on the average, the performance under VP/ix-Simultask386
with 2 users seems about that of an 8 MHz PC/AT, but the variance is
*very* large depending on the sort of work the program does.  Possibly
just as important, however, is that it doesn't kill the performance
of the rest of the system to have a few DOS tasks running.  (I have
not yet done testing with a large numbe of  DOS tasks.)

>    If any of you who have this equipment could do this it would be
>greatly appreciated by those of us who are investigating getting some
>of this type of systems.
>    Thanks in advance for your insights....
>-- 
> Guerry A. Semones                 BITNET: drogo at tucc.BITNET
> Information Services              USENET: gas at ecsvax
> Duke University                   My views are despairingly mine only.
> Talent Identification Program     "We ain't gifted, we just work here."

-- 
 Marc Mengel	

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