Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!portal!cup.portal.com!jxh
From: jxh@cup.portal.com (Jim - Hickstein)
Newsgroups: comp.windows.ms
Subject: Re: MS Windows questions
Message-ID: <16900@cup.portal.com>
Date: 9 Apr 89 02:48:31 GMT
References: <134000002@silver>
Distribution: na
Organization: The Portal System (TM)
Lines: 35


 > It doesn't seem right that
 > a program that is SUPPOSEDLY optimized for the 286 can't access this extra
 > memory.

Who said anything about "optimized"?  In my experience, Windows/386 (the same
arguments apply) consists of just barely enough 386 code to get WIN86.COM to
run in one virtual-86 machine while allowing other non-windows apps to run
in other virtual machines.  WIN86.COM itself has nothing that I can detect
specific to the 386 that would make it run faster or better, like 32-bit
instructions just to name one.  Optimized?  Hardly.

In fairness, though, the 80286 doesn't have this virtual-8086 feature of the
386, and can only use physical addresses greater than 20 bits in protected
mode.  Now, I can imagine running WIN86.COM in protected mode, managing
segment descriptors by trapping the right exception and emulating the real-
mode behavior that WIN86.COM expects, but that, frankly, is a lot more work.
Plus, it will run a bit slower (arguably much slower; depends on whose
benchmarks you believe) in protected mode versus real mode for a given set
of instructions.

Generally, if you can think of a good way to do something and an easy way,
I'll give you one guess which way Microsoft is going to do it.

Anyway, you may be able to get someone else's expanded memory emulator to
switch to protected mode and copy to and from that extra RAM, so Windows
need not be bothered about the actual mechanism.  Expect this to have a
performance penalty, but probably less than swapping those segments to
disk...  Sorry I can't offer a concrete suggestion about whose product
does this, but I'm sure it's out there, somewhere.  Somebody else please
take over here.

-Jim Hickstein
jxh@cup.portal.com
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