From: lubaldo AT adinet DOT com DOT uy
Message-Id: <3.0.1.32.19980130203727.006c24f8@adinet.com.uy>
Date: Fri, 30 Jan 1998 20:37:27 -0300
To: djgpp AT delorie DOT com
Subject: Physical memory, virtual memory. DJGPP+CWSDPMI, how they work?
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	Hello everyone! I think this is on-topic... if it is not... sorry.

	I would like to know how physical memory and virtual memory works using
CWSDPMI and DJGPP. I want to know this only for curiosity... but maybe this
helps someone or someone has the same curiosity...

	Suppose I have a computer with 2 mb free of memory, DOS 6.22 and CWSDPMI
as DPMI provider. Suppose I have a program (compiled with DJGPP) that it
has 1mb of code and 2mb of music and bitmaps. Ok, this are my questions:

	1- Suppose I load all the program and the music and the bitmaps on the
startup. Then, I use only 1mb of the music and the bitmaps in a first
stage, so the 2mb of the free memory are full with 1mb of code and 1mb of
data. The question is: what happens when the program enters in a 2nd stage
where I use the same 1mb of code but the other 1mb of the data?
		- The previous data is stored in virtual memory and the other data (the
one that it is used now and has not been used before) is loaded in memory?
		- The previous data is leaved in memory and the other (new) data is
readed from virtual memory?

	2- CWSDPMI or DJGPP has something to optimize the speed when all the
physical memory is not suficient to hold all the data (something like a
cache?)?

	When I say virtual memory I am saying the memory that it is simulated
using the harddisk.
	I hope I was clear, because is difficult to me write in English.
	Ok, TIA and goodbye!

P.s: I know: if I do a program I will not load all the data that is not
necessary at startup until the data is necessary and also I will free from
memory the data that is not used anymore, but I want to know only.


Ivan Baldo:
lubaldo AT adinet DOT com DOT uy - http://members.xoom.com/baldo.
Phone: (598) (2) 613 3223.
Caldas 1781, Malvin, Montevideo, Uruguay, South America.

(If you have problems with the previous addresses, try this ones:
ibaldo AT usa DOT net, http://baldo.home.ml.org).