Path: utzoo!utgpu!attcan!uunet!lll-winken!ames!mailrus!cornell!uw-beaver!microsoft!philba
From: philba@microsoft.UUCP (Phil Barrett)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Using XMS driver (HIMEM) & VDISK???
Message-ID: <207@microsoft.UUCP>
Date: 6 Jan 89 21:03:08 GMT
References: <499@igor.Rational.COM> <6478@killer.DALLAS.TX.US> <3173@ncrwic.Wichita.NCR.COM> <1586@micomvax.UUCP>
Reply-To: philba@microsoft.UUCP (Phil Barrett)
Organization: Microsoft Corp., Redmond WA
Lines: 18

I am only speaking for myself, not Microsoft but the point of XMS isn't
to create an unnecessary standard but rather to provide a way for applications
to co-operatively use extended memory AND provide a machine independent
mechanism for accessing it.  The simple fact is that there are a lot of
machines out there with different mechanisms for switching A20 and switching
modes (real <--> protected).  An additional problem occurs with the top-down
allocation scheme in that there is no way to free up space (if you aren't the
last guy on the Int 15h chain).   XMS addresses these.

As to the complaint that this is a useless standard, lots of real mode apps,
drivers, TSRs will use extended memory (particularly for the High Memory 
Area -- 1-st 64K-16 bytes of extended memory).  I know of at least 6 that
are (or will soon be) available.  This would lead to chaos if not dealt with
in standard fashion.  That is why I believe that the XMS spec is a good thing.


Phil Barrett
Microsoft Corp.