Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!ames!purdue!norman
From: norman@cs.purdue.EDU (Victor Todd Norman)
Newsgroups: comp.sys.transputer
Subject: Dynamically determining memory size
Message-ID: <9298@medusa.cs.purdue.edu>
Date: 17 Jan 90 22:31:46 GMT
Organization: Department of Computer Science, Purdue University
Lines: 22

Question:  Is there a way for a program to dynamically figure out how
large the memory space is?  I have tried to figure out this value by
having my program write a value to memory and then read it back,
checking if the value is the same.  I start doing this somewhere
that I know exists and try to walk off the end of memory.  I was
hoping that as soon as I fell off the end, the value would be changed.
But, this doesn't work since, as I've found out, memory seems to wrap
around.

Example:
	I am using a T414 (2K on-chip) with 2M external memory.
Thus, the highest address is #80200800.  But, when I write a value to
somewhere off in never-never land, like #802037be, I can read the
value back from that location.  Or, I can find the value in #800037be
(which is where it actually exists all along).

So, my idea of checking legal addresses by writing to them doesn't
seem to work too well.  

Any suggestions?

Victor Norman