Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!bellcore!uunet!sdrc!thor!scjones
From: scjones@thor.UUCP (Larry Jones)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: EMS hardware vs. software emulation
Message-ID: <103@thor.UUCP>
Date: 8 Jan 91 21:26:45 GMT
References: <37694@cup.portal.com>
Organization: SDRC, Cincinnati
Lines: 19

In article <37694@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes:
> It seems to me that anyone who designs a system with a 286, 386, or 486
> with more than 1M of memory should include hardware EMS registers and mapping
> logic, unless he only plans to run Unix.  At first, I thought maybe only
> the 286 needs it, because the other chips have paging.  But then I remembered
> that all the DOS people run in real-address mode, so the paging mechanism
> is disabled.  The only way around this would be to run your DOS applications
> in virtual-8086 mode, but I don't think anybody does that, do they?

You were right the first time -- the 386 and 486 paging mechanism works
quite well for doing EMS.  Both 386^Max and QEMM provide EMS memory by
running DOS in virtual-86 mode and using the paging registers.  That's
why none of the chipsets have EMS registers.
----
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