Mailer: WinNET Mail, v1.0
Newsgroups: bit.listserv.win3-l
Date:         Wed, 23 Dec 1992 17:25:11 -0600
Reply-To:     "Conrad J. Sabatier" <csabatier@nola.win.net>
From:         "Conrad J. Sabatier" <csabatier@NOLA.WIN.NET>
Subject:      Re: Slow SCSI disk in Windows 3.1 Enh mode

> >Date:  19 December 1992 08:38 est
> >From:  NATHAN BRINDLE <NBRINDLE%INDYCMS.BITNET at PUCC.PRINCETON.EDU>
> >Subject:  Re: Slow SCSI disk in Windows 3.1 Enh mode
>
> >>On Fri, 18 Dec 1992 10:45:49 EST NATHAN BRINDLE said:
> >>>Seriously, folks ought to do a <little> research before posting replies
> >>>like Wael did.  Telling someone to delete SMARTDRV from their CONFIG.SYS
> >>>because it also shows up to be executed in AUTOEXEC.BAT could potentially
> >>>cause the poor questioner a LOT of trouble.
> >>
> >> Could you please tell us what kind of trouble you expect from stopping
> >> a file from being loaded twice? I just deleted mine, and could see no
> >> apparent problem. But maybe there will be....?
> >>
> >> Morten
> >>
> >That's my point.  I <don't know>.  Note above I said <potentially>.  If
> >SMARTDRV has been caching in double_buffer mode for SCSI all along, it
> >may not take too well to not double buffering anymore.  I would be afraid
> >of corrupting my data or losing it altogether if I were to delete something
> >from the startup configuration that SMARTDRV needs when it is running.
> >
> >I see a lot of "advice" come across this list that too much of the time ends
> >up being refuted by someone who knows better.  All I'm asking is that people
> >take a little more time with their answers and make sure they know what
> they're
> >talking about before they post.  I didn't post a solution; I posted a warning
> >based on a feeling that Microsoft wouldn't set you up that way unless there
> >was a reason.  I know that's not always the case :) but I'm leaving well
> enough
> >alone.  Maybe someone from Microsoft ought to jump in here and give us an
> >explanation?
>
>I'm not from Microsoft, but I can offer an explanation.  Many SCSI
>controllers user direct memory access techniques to provide the I/O
>service.  The controller has a processor that reads directly from or
>writes directly to a buffer area that is in the Intel processors real
>memory and virtual address space.  Windows uses a double buffering
>technique so that it doesn't interfere with what the controller
>processor is doing.
>
>The way that SMARTDRV was designed requires some of its environment to
>be set up specially for certain options *before* it is run.  Thus the
>config.sys entry allows SMARTDRV a chance to construct such an
>environment change.  (The double_buffer option is one of those options
>that needs it.)  So, it's necessary to specify that you want double
>buffering via the config.sys entry.  When SMARTDRV is invoked from the
>command line, it sees the modified environment and runs the wanted
>option(s).
>
>It is possible that with certain SCSI DMA controllers and Windows
>running without double buffering, that you can get you input and/or
>output pretty badly scrambled while its coming and/or going.  Could
>cause quite a mess.  If you are lucky the scrambling is so bad that you
>don't get very far before everything grinds to a halt.  However, you've
>got no real insurance that the failure mode will be so innocuous.
>Yep......  you *could* be in a *real* mess if you had the unlucky
>combination of SCSI controller characteristics and particular
>application execution characteristics.
>
>Vince
>
If I may add my voice to this, in browsing through the Microsoft
Windows Resource Kit manual today, I found the explanation for
this.  According to the book, the line:

device=smartdrv.exe /double_buffer

in CONFIG.SYS, installs ONLY the double buffer driver, not the
cache. The cache must be installed in AUTOEXEC.BAT.

Conrad


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Conrad J. Sabatier      Internet:csabatier@nola.win.net
P.O. Box 641303
Kenner, LA  70064-1303  Windows is to DOS as Color is to B&W, as
(504) 568-9202          Automatic is to Standard, as CD is to vinyl,
                        as ... (your analogy here)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU