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From: joonsong@tornado.Berkeley.EDU (Suk-Hyun Song)
Newsgroups: comp.windows.ms
Subject: Re: Running non-windows applications in windows 3.0
Message-ID: <1990Aug8.203906.27896@agate.berkeley.edu>
Date: 8 Aug 90 20:39:06 GMT
References: <4162@dogie.macc.wisc.edu>
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Reply-To: joonsong@tornado.Berkeley.EDU (Joon Song)
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In article <4162@dogie.macc.wisc.edu> pschwart@vms.macc.wisc.edu (Paul Schwartz) writes:
>>When you are running in 386 enhanced mode, virtual memory is turned on.
>>Hence, Windows reports that you have 800k of memory left.  Unforuntunately,
>>non-windows applications can not run in virtual memory.  Windows must
>>allocate physical memory to those applications.  On your 2 meg system,
>>you only have a bit over 1 meg left after Windows is loaded.  So there
>>is no way for you to run 2 640K dos windows.
>> 
>
>This is not true.  I have a 386 with 4 megs of RAM and I can open 16 DOS boxes
>before running out of memory, much more than the 4 megs of actual memory that
>I have avaliable.  I think windows can swap inactive DOS boxes to virtual.  
>My hypotheis as to why you run out of memory is because windows saves some of
>that memory for itself.  When windows apps like paintbrush, write, and notebook
>get minimized, only a portion of their code stays in memory.  DOS boxes when
>minimized don't free up any memory, therefore there is no memory avaliable 
>for windows functions (some of the 386 management stuff takes heafty memory
>space).  Also, windows does some weird stuff as to where in memory it sticks 
>things.  Perhaps there is no contiguous block free for a new DOS box.

Non-windows applications must be run in physical memory.  They can not run in
virtual memory as can Windows applications.  However if a non-Windows program
is configured to not run in the background, they can be swapped to disk when
they are not in the foreground.  You can open as many of these DOS boxes as
the swapfile can hold.  But only one of these can be run at a time, and I 
didn't buy a 386 to have DOS boxes swapped to disk.  I could done that just
as easily with a 286.  One of the main advantages of the 386 is that it 
supports demand paged memory.  But this feature is not available for non-
Windows applications.

If you want to multitask non-Windows applications, you must have enough 
memory to keep all of the programs in physical memory.  It doesn't matter
how much virtual memory you have.  

So, my point that you can't multitask two 640K non-Windows applications on a 
2 meg system is still valid.  Non-windows applications can not run in virtual
memory.

    Joon Song
    joonsong@ocf.berkeley.edu