From: "Johnny Chan" <johnny_chan AT phoenix DOT com>
To: <djgpp AT delorie DOT com>
Subject: How to browse thru all the Physical RAM installed
Date: Tue, 28 Sep 1999 11:57:00 -0700
Message-ID: <000301bf09e3$3fa705c0$ae3d7a86@phoenix.com>
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Reply-To: djgpp AT delorie DOT com

I am new in Protected mode programming. Here is my question:

I want to know how to browse thru all the phyiscal RAM I had installed in
the system.
I am writing a diagnostic program in MSDOS using DJGPP and WDOSX to verify a
network server device. This device requires anything from 500MB to 1GB of
physical memory. I am trying to develop some software to hack on those
physical memory to sniff the activities on the RAM. This is a controlled
enviornment, no HIMEM nor EMM386. plain MSDOS.

Somebody suggest me to use near ptr:

if (__djgpp_nearptr_enable())
{
  x=(char *)(__djgpp_conventional_base);
  printf ("%.8lX\n", __djgpp_conventional_base);
  for (i=0; i<800000h; i++)	// read first 8MB
    printf ("%X ", x[i]);
  __djgpp_nearptr_disable();
}

I tried this code in my 16MB computer and __djgpp_conventional_base shows
FFBFF3C1h. Anybody people know why it is FFBFF3C1h? I wonder if this really
can access to the full 4GB RAM?
Do you know any DOS-like 32bit debug.exe I can use? any sample code on this
area?

Also, I wonder how I can map all the RAM I have on the system (for example
2GB RAM) as the logical linear memory so that my program can access it using
the near ptr?

Finally, as we all known, there are IO.SYS, MSDOS.SYS, COMMAND.COM, drivers,
and ther DPMI clients reside on the memory. where can I get the memory
mapping directory? Anybody have sample code or suggestion on this?
--jC