Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!usc!samsung!uunet!ns-mx!umaxc.weeg.uiowa.edu!williams From: williams@umaxc.weeg.uiowa.edu (Kent Williams) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: XMS -> EMS without using protected mode? Message-ID: <3864@ns-mx.uiowa.edu> Date: 10 Jan 91 20:20:34 GMT References: <4602@ruuinf.cs.ruu.nl> <22515@well.sf.ca.us> Sender: news@ns-mx.uiowa.edu Reply-To: williams@umaxc.weeg.uiowa.edu (Kent Williams) Organization: U of Iowa, Iowa City, IA Lines: 43 In article blk@mitre.org (Brian L. Kahn) writes: > >I would like to convert some XMS memory to EMS, without using >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. The VLSI and C&T chipsets have hardware that can enable RAM on a page by page basis throughout the Processor's address space. TLB works by mapping in RAM to the holes between the ROMS, on top of graphics RAM when you're not using Graphics, etc. >I have seen a manager called LASTBYTE that claims to >do this by twiddling the chipset DMA's or something, but LASTBYTE >won't run on my machine. I do have the kind of chipset they support, >so I bet my hardware could do this with the right software. The two sentences contradict each other. Try the latest version off of SIMTEL20, V1.17. It understands nearly all C&T chipsets for 286 and 386, and has recently added support for a VLSI chipset. It comes with a test program that can tell you whether it will work with your computer. This program is available in a separate smaller ZIP file, so you don't waste time downloading the whole thing if it won't work. >Unfortunately, I don't understand what is in some chipsets (NEAT, >VLSI, others) that allow this operation, so I am a bit in the dark. >Can anyone either explain the special features of chipsets, explain >what is needed for XMS -> EMS, or point me to some software? > >-- >B< Brian Kahn blk@security.mitre.org "may the farce be with you" There are commercial products that simulate EMS using expanded memory, but they're an order of magnitude slower than the real thing. & for all you 'The Cuckoo's Egg' fans, our friend Brian works at Mitre -- a company featured prominently in that book. -- Kent Williams --- williams@umaxc.weeg.uiowa.edu "'Is this heaven?' --- 'No, this is Iowa'" - from the movie "Field of Dreams" "This isn't heaven, ... this is Cleveland" - Harry Allard, in "The Stupids Die"