Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!sjsca4!poffen From: poffen@sj.ate.slb.com (Russ Poffenberger) Newsgroups: comp.os.msdos.misc Subject: Re: Little-known DOS Extender for 286/386/386sx's Message-ID: <1990Aug15.232458.22819@sj.ate.slb.com> Date: 15 Aug 90 23:24:58 GMT References: <2411@crdos1.crd.ge.COM> Reply-To: poffen@sj.ate.slb.com (Russ Poffenberger) Organization: Schlumberger Technologies, San Jose, CA. Lines: 32 In article liberato%drivax@uunet.uu.net (Jimmy Liberato) writes: >DLEWIS@SCU.BITNET (Dan Lewis) writes: > >>... >>Unlike all other such products, however, LASTBYTE has the unique >>ability to use *ALL* 384k of that memory! Physical memory that sits >>"behind" the display buffer, ROM's, etc., is not accessible with other >>DOS extenders, but LASTBYTE uses a "bank-switching" technique to store >>data there (e.g., for a ram disk, emulated EMS memory, etc.). >>... > >What on earth does "physical memory that sits 'behind' the display buffer..." >mean? I understand how rom shadowing is done on 386 and NEAT 286 machines by >remapping unused extended memory onto the bios adresses and how memory managers >can find vacant addreses in upper memory to map extended memory into to allow >hiloading of TSRs, drivers, and even the operating system kernal but you seem >to be saying that, for example, I can have an EMS page frame at the same address >as my video buffer through some sort of "bank-switching" (multiplexing?). >Either I am completely misreading what you are saying or your method is indeed >"little-known." Please elaborate! > Supposedly, in the C&T chipset, if you have more than 1Meg of memory, extended memory IS NOT remapped into the 640K to 1M memory space, rather conventional memory is really there, however disabled except for rom shadowing as supported by the chipset. Russ Poffenberger DOMAIN: poffen@sj.ate.slb.com Schlumberger Technologies UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen 1601 Technology Drive CIS: 72401,276 San Jose, Ca. 95110 (408)437-5254