Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hpcvlx!bturner
From: bturner@hpcvlx.HP.COM (Bill Turner)
Newsgroups: comp.windows.ms
Subject: Re: Expanded / Extended memory
Message-ID: <106580044@hpcvlx.HP.COM>
Date: 13 Jun 89 17:20:04 GMT
References: <11885@netnews.upenn.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 17

> The configuration that works best for Windows won't work for OS/2.  In their
> infinitly grand way of doing things, Windows uses expanded memory, OS2 uses
> extended memory.  I'm not sure why Microsoft (or IBM?) did this, but that's
> how it is.  I believe that Unix uses extended memory also.

The reason for this is that Windows is running under MS-DOS, and therefore in
real (8086) mode, while OS/2 is more of a "real" operating system, and uses the
protect mode of the '286.

Expanded memory allows hardware to bankswitch memory under the 1MB limit of
real mode, while extended memory IS protect-mode memory, above the 1MB limit.

(It also helps to consider the history of MSWindows -- when it was originally
to be released, the AT was not yet released...)

--Bill Turner (bturner@hp-pcd.hp.com)
HP Corvallis Information Systems