Path: utzoo!attcan!lsuc!maccs!cs4g6ag
From: cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: ramdisks in extended memory, xms, and ems
Message-ID: <25756BEB.26629@maccs.dcss.mcmaster.ca>
Date: 30 Nov 89 18:05:31 GMT
References: <436@wjh12.harvard.edu>
Reply-To: cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn)
Distribution: na
Organization: McMaster University, Hamilton, Ontario
Lines: 24

In article <436@wjh12.harvard.edu> djb@wjh12.UUCP (David J. Birnbaum) writes:
$Is there any way to decide among setting up ramdisks in plain
$old extended memory, xms extended memory, or ems?

   Yes.  Put it in expanded (LIM EMS) memory.  It will run faster there.
To access extended memory, you have to
a) kick the processor into protected mode
b) do the transfer
c) reset the processor (!)

because Intel didn't provide any other way to get a 286 back to real
(8086) mode after being in protected mode.  This takes lots of time.
On the other hand, to access expanded memory, you have to
a) tell the EMM what page(s) you want to use
b) do the transfer

   This applies to disk caches, too:  if you have a choice between putting
them in extended or expanded memory, use the expanded.

-- 
Stephen M. Dunn                               cs4g6ag@maccs.dcss.mcmaster.ca
          <std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
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