Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!helios.physics.utoronto.ca!ists!yunexus!xrtll!silver
From: silver@xrtll.uucp (Hi Ho Silver)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: XMS to EMS driver wanted
Message-ID: <1990Dec29.173158.25522@xrtll.uucp>
Date: 29 Dec 90 17:31:58 GMT
References: <999@pdxgate.UUCP>
Reply-To: silver@xrtll.UUCP (Hi Ho Silver)
Organization: Not around here, pal!
Lines: 24

In article <999@pdxgate.UUCP> berggren@eecs.cs.pdx.edu (Eric Berggren) writes:
$  I would like a driver (commercial or PD) to be able to automatically 
$address part of my extended memory in to UMB as conventional LIM EMS 3.2
$(or even 4.0, if possible) for my 286 machine. Most of the drivers I have
$seen, does 4.0 requiring a 386 (>sigh<). Any help would be appreciated.

   Unless your hardware supports accessing this memory as expanded, your
only choice is a program which steals a 64K chunk of main memory and
physically copies data back and forth between it and your extended memory.
PC Magazine has such a program (EMS40.SYS).  But be forewarned that it's
painfully slow, since it doesn't just remap the memory, it actually copies
it, and that you'll lose about 70K of conventional (the first 640K) memory
(64K for the page frame plus whatever the driver takes up).

   The reason you see so many drivers for the 386 is that its memory
management hardware includes the ability to map 4K chunks of memory from
anywhere in its address space to anywhere else.  This makes it relatively
easy to write an EMS simulator - the CPU does almost all of the work for
you.
-- 
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