Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!drivax!liberato From: liberato@dri.com (Jimmy Liberato) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: XMS -> EMS without using protected mode? Message-ID: Date: 13 Jan 91 10:51:40 GMT References: <4602@ruuinf.cs.ruu.nl> <22515@well.sf.ca.us> <3864@ns-mx.uiowa.edu> Reply-To: liberato@dri.com (Jimmy Liberato) Organization: Digital Research, Inc., Monterey Development Center Lines: 30 williams@umaxc.weeg.uiowa.edu (Kent Williams) writes: >In article blk@mitre.org (Brian L. Kahn) writes: >> >>I would like to convert some XMS memory to EMS, without using >>protected mode. Isn't XMS memory XMS memory by virtue of being defined as such by an XMS driver? And isn't XMS by its nature in protected mode? >That isn't exactly what it does -- it uses the integrated chipset mapping >hardware to make use of the memory 'behind' the ROMS and video ram between >640K and 1 MByte. ^^^^^^ ^^^^^^ I keep hearing this metaphor but it does nothing to make this clear to me. If anything the "behindness" happens AFTER the shadow remapping. There is no memory to be made use of by the chipset in the ROM and video address areas. Am I misinterpreting your terminology? Can you elaborate? >There are commercial products that simulate EMS using expanded memory, but >they're an order of magnitude slower than the real thing. But EMS=expanded memory! You must have meant to type extended memory. Those programs are really only for early 286 class machines and their slowness and inadequacy is a reflection of the awkward way the 286 handles extended memory. Those EMS emulators are not needed with modern NEAT 286 or 386/486 systems. -- Jimmy Liberato liberato@dri.com ...uunet!drivax!liberato