Undocumented phenomenon?

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#523

From: Victor Todd Norman
Date: Tue, 27 Mar 1990 21:42

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I have noticed something that I don't believe appears anywhere in any
documentation.  Here's the situation:

I have one high priority process running on my T414B.  This process
looks at the special "register save area" (see p. 79 of Compiler
Writers' Guide), and sees NotProcess.p (0x80000000) in WdescIntSaveLoc
(thus, no low priority process was interrupted).  Then, the process
executes an IN instruction, and then looks again at WdescIntSaveLoc,
and now the value has been changed to 0x80000001 (the low bit has been
set).

I supposed there is a good reason for this?, or is my hardware acting funny...

I have noticed that this only happens if the process doing the IN (or
OUT) is running at high priority.

Victor Norman

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!purdue!norman
From: norman@cs.purdue.EDU (Victor Todd Norman)
Newsgroups: comp.sys.transputer
Subject: Undocumented phenomenon?
Message-ID: <10145@medusa.cs.purdue.edu>
Date: 27 Mar 90 21:42:32 GMT
Organization: Department of Computer Science, Purdue University
Lines: 17