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From: kls30@duts.ccc.amdahl.com (Kent L Shephard)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: EMS hardware vs. software emulation
Message-ID: <69Nf027I04Hr01@JUTS.ccc.amdahl.com>
Date: 8 Jan 91 17:58:19 GMT
References: <37694@cup.portal.com>
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Reply-To: kls30@DUTS.ccc.amdahl.com (Kent L. Shephard)
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Organization: Amdahl Corporation, Sunnyvale CA
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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?

Any good multitasking env. does.  ie - Windows and DESQview.  There is no
need for those registers on a 386 only on a 286 or less.

>
>Am I right?  Is omission of the EMS hardware in a 2/3/486 >1M system
>a cardinal sin?  The reason I ask is that there are chipsets on the
>market for building PC-compatible system boards with for example
>a 386 and 16M but don't have hardware EMS.  Does that mean any memory
>above 1M is mostly useless (i.e. real slow due to software EMS emulation)?

Don't worry about it being supported in the chipset or bios.  Qemm will
do fine on 386s - memory management is in the hardware.
--
/*  -The opinions expressed are my own, not my employers.    */
/*      For I can only express my own opinions.              */
/*                                                           */
/*   Kent L. Shephard  : email - kls30@DUTS.ccc.amdahl.com   */