Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!rochester!rit!tropix!moscom!ur-valhalla!uhura.cc.rochester.edu!sunybcs!rutgers!att!cbnewsc!psfales
From: psfales@cbnewsc.ATT.COM (Peter Fales)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: EMS Extended to Expanded RAM emulator
Keywords: ems, ram, emulator
Message-ID: <1291@cbnewsc.ATT.COM>
Date: 22 Jul 89 19:49:48 GMT
References: <312@ohs.UUCP>
Organization: AT&T Bell Laboratories
Lines: 26

In article <312@ohs.UUCP>, mday@ohs.UUCP (Matthew T. Day) writes:
> I have recently downloaded a program called EMS40 from a local BBS, and I
> would like to know how and if it works.  What it supposedly does is emulate
> an EMS board, thereby making your extended memory into expanded RAM.  Since
> here on my IBM/AT I have 512K main and 512K extended, I would like to somehow
> tack that extended memory in with my main.  Currently I'm using it as a RAM
> disk with VDISK.SYS, but to be able to move myself up to at least 640K would
> be wonderful.  Has anyone got an idea on either how EMS would work for me or
> another application that I could use?

I raised the question a while back and I believe the consensus then was:
No, you cannot use software to map extended memory into the 0-640K range.

The way these programs work is by stealing a 64K block of memory from the
640K (in your case 512K) to use as "bank switched" memory.  Then as your
RAMDISK (or whatever) needs access to extended memory, 16K blocks are
copied between main memory and extended memory.

This is much slower than the hardware bank switching used by true EMS
boards, but it does provide a standard interface to extended memory
for any program which can use EMS.
-- 
Peter Fales			AT&T, Room 5B-420
				2000 N. Naperville Rd.
UUCP:	...att!ihlpb!psfales	Naperville, IL 60566
Domain: psfales@ihlpb.att.com	work:	(312) 979-8031