From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] delay and aamloop
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Message-Id: <20020127192032.87D9B19988@mail.cse.psu.edu>
Date: Sun, 27 Jan 2002 14:20:30 -0500
Topicbox-Message-UUID: 46de961c-eaca-11e9-9e20-41e7f4b1d025

AAM is "ascii adjust AX after multiply", which may
well have been on the 80186.  It fools with AX but
that's about it.

You didn't actually replace AAM, you replaced the
entire call to delay(), which does some other stuff
first.

I bet if you replace AAM with some other
hopefully-single-cycle instruction, like XOR AX, AX,
you'll still get the memory changing behavior,
which will clear AAM's good name.

However, it could be that the Medium structure
has somehow gotten in the way of the stack,
and calling delay is just enough to overwrite the name.

In floppyinitdev try adding

	print("floppy name %s=%lux\n", mp->name, mp->name);

and in floppyrevive:

	print("floppyrevive stack at &dp=%lux\n", &dp);

and see if the two numbers are dangerously close.

Russ