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From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] delay and aamloop
Date: Sun, 27 Jan 2002 14:20:30 -0500	[thread overview]
Message-ID: <20020127192032.87D9B19988@mail.cse.psu.edu> (raw)

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


             reply	other threads:[~2002-01-27 19:20 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-01-27 19:20 Russ Cox [this message]
2002-01-28  5:50 ` Lucio De Re
  -- strict thread matches above, loose matches on Subject: below --
2002-01-27 13:55 Lucio De Re

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