Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!lll-winken!elroy.jpl.nasa.gov!usc!samsung!rex!ames!vsi1!octopus!stever
From: stever@Octopus.COM (Steve Resnick )
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Re: adding to the heap?
Message-ID: <1990Mar13.191242.29304@Octopus.COM>
Date: 13 Mar 90 19:12:42 GMT
References: <9898@batcomputer.tn.cornell.edu>
Reply-To: stever@octopus.UUCP (Steve Resnick )
Distribution: usa
Organization: Octopus Enterprises, Cupertino CA
Lines: 19

In article <9898@batcomputer.tn.cornell.edu> braner@tcgould.tn.cornell.edu (Moshe Braner) writes:
>and even the first
>64K (minus 16 bytes) of extended RAM, which supposedly you can cheat
>and read from "real" mode (using the segment FFFFH, offsets over 000FH
>- is that really possible?).

It is really possible on some machines which have a way to toggle the A20
line on the CPU address bus. Normally this is disabled. The problem with
using memory between FFFF:10 and FFFF:FFFF is that other programs may assume
this memory is usable, including TSR's and device drivers..Microsoft, Lotus,
Intel and AST Research came up with an eXtended Memory Specification (XMS)
which MS has drivers free for the asking. Just call 'em up and they will send
you a manual and diskette describing the specification and provding a device driver
which implements the XMS 2.0 specification (Which is similar in function to EMS)
They also include source code for those interested assembler hackers... :)


Steve