Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!philmtl!ray From: ray@philmtl.philips.ca (Ray Dunn) Newsgroups: comp.sys.ibm.pc Subject: Re: weakness in the LIM EMS 4.0 spec Message-ID: <986@philmtl.philips.ca> Date: 2 Feb 90 18:19:17 GMT References: <28980@amdcad.AMD.COM> Organization: Philips Electronics Ltd. Product Group PC. Montreal. Lines: 37 In referenced article, phil@pepsi.amd.com (phil ngai) writes: > >Well, guess what. This driver simply grabs 64 Kbytes of conventional >memory, calls it the memory buffer, and implements EMS by going into >protected mode and shuffling data back and forth to extended memory. >.... >With standards like this, who needs standards? You are not describing a deficiency in the *standard*, you have found what might be initially considered a poor or restricted *implementation* of the standard. However, you are describing a *software only* implementation that gives you EMS on a machine that has no hardware to support it. In effect it is an *emulation* of EMS memory using 286 extended memory, and as such can be extremely useful. A similar implementation of EMS can be done (and has been) on an XT machine using swapping to disk. I may be wrong, but doesn't another popular but multi-tasking operating system also use hidden memory/disk swaps? (:-). [Yes I do understand that automatic paging a-la-UNIX is infinitely more program friendly than the simple but awkward to use application controlled memory paging of LIM 4.0] The *speed* of an EMS implementation, is of course something that an application program can do little about, however the other complaint, the fact that it used a maximum of only one 64K page, can of course be detected by the application which could modify its behaviour accordingly. The fact that the standard allows a wide variation in the window and physical memory availability is, of course, because of the wide variation in the physical hardware on which the standard is defined to run. -- Ray Dunn. | UUCP: ray@philmtl.philips.ca Philips Electronics Ltd. | ..!{uunet|philapd|philabs}!philmtl!ray 600 Dr Frederik Philips Blvd | TEL : (514) 744-8200 Ext : 2347 (Phonemail) St Laurent. Quebec. H4M 2S9 | FAX : (514) 744-6455 TLX : 05-824090