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From: cbenda@unccvax.UUCP (carl m benda)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 386 on PC (repost)
Message-ID: <780@unccvax.UUCP>
Date: Tue, 28-Jul-87 19:56:32 EDT
Article-I.D.: unccvax.780
Posted: Tue Jul 28 19:56:32 1987
Date-Received: Thu, 30-Jul-87 04:04:31 EDT
References: <17248AHS@PSUVM>
Organization: Univ. of NC at Charlotte, Charlotte, NC
Lines: 46
Summary: 8086 can only address one (1) meg.

In article <17248AHS@PSUVM>, AHS@PSUVM.BITNET writes:
>      
> I made a mistake in my previous note.  Expanded memory is limited to
> 8 Megabytes if you use EMS expansion cards such as Intel or AST.
> However, Desqview, using the 386 built-in memory management
> services, will create an upto 16-Megabyte virtual EMS for *each* virtual
> *concurrent* 8086 machine awaken from the 386 by Desqview.  Further, each
> of these virtual EMS memories is 32-bit memory since the 386 build them
> from the CPU own's 32-bit memory.

You've made more than one mistake... the EMS expansion cards you are 
talking about work off of a 16bit data path IF they use the AT bus, and
only an 8 bit data path if they work on a pc what this means is that
the EMS memory is only 16 bit or 8 bit respectively.

> 1..  Insert in an empty slot an Everex "286 board for PCs".  That will
> give you an 8-Mhz no-waitstate 80286 with 640k of dedicated 16-bit
> memory.  Cost: 400$ list, 275$ by mail.  By now, you are already

Sorry, PC disk I/O lossage means that in real terms the PC with its 4MHz
bus will never ever come close to the performance of an AT unless you trash
everything but the powersupply.

> called "virtual 8086".  DesqView will generate up to 256 totally
> independent and multitasking virtual 8086/8088 PC-DOS sessions.
> Further, each separate session can use its own dedicated 16 Megabytes
> of Enhanced (EEMS) or regular Expanded Memory (EMS).  Naturally, each

Are you sure about that?? As you may know, an 8086 can itself can only
address 1 ONE Megabyte of whatever... rom, ram, I/O.  It takes SPECIAL
hard ware known in some circles as EMS, (I perfer the apple ][ term of
banked switched memory), to allow the 8086 in the PC to address more than
one megabyte.  If the Everex card has this hardware built into it, like the
afore mentioned AST card then you are all set, if not, then your addressing
limit is 1 megabyte! (for each and every virtual 8086 you've set up).





> Michel
>      
> <Fin><End>
/
/Carl
....decvax!mcnc!unccvax!cbenda