Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!njin!njitgw.njit.edu!mars.njit.edu!cd5340 From: cd5340@mars.njit.edu (David Charlap) Newsgroups: comp.os.msdos.apps Subject: Re: QEMM, etc Recommendation Sought Message-ID: <1991Mar28.053336.29004@njitgw.njit.edu> Date: 28 Mar 91 05:33:36 GMT References: <4734@gumby.Altos.COM> Sender: root@njitgw.njit.edu (System PRIVILEGED Account) Organization: New Jersey Institute of Technology Lines: 36 Nntp-Posting-Host: mars.njit.edu In article valley@uchicago (Doug Dougherty) writes: >jerry@gumby.Altos.COM (Jerry Gardner) writes: > >>In article ersys!davem@nro.cs.athabascau.ca (Dave McCrady) writes: > >>> Extended memory can't be mapped to high ram. > >>This is an incorrect statement. On a 386 machine, QEMM does map extended >>memory to high RAM. ... ... ... A 386 running in protected mode can remap >>RAM in any location to any other location. > >This is nitpicking. Actually, what happens is that the 386 memory >manager emulates expanded memory in software, using the memory mapping >capabilities of the processor. Then the expanded memory is used as >"high ram". But the point is, it is true expanded memory. > >It is definitely the case that extended memory (qua extended memory) >can't be mapped to high ram. Let's try this yet again... Expanded memory (EMM, LIM, QEMM, whatever) is only a standard for protocols, with no regard for hardware that will impliment it. Expanded memory can exist on a RAM card which maps into High-memory, it can be 386 protected mode remapping extended RAM onto low-memory, or it can be a disk-swap algorithm. Anything that swaps memory in and out of the real-mode address space according to the spec laid out by Lotus/Intel/Microsoft is true EMM. As for mapping extended RAM. Any chip 80386 or higher can use its protected mode to remap any region of its address space to any other region of its space. That's part of what goes into creating a virtual XT with the 386 (as VM/386 does). The 286 can also, but in a much more limited way - which won't work in real-mode. -- David Charlap "Invention is the mother of necessity" cd5340@mars.njit.edu "Necessity is a mother" Operators are standing by "mother!" - Daffy Duck