Article View: comp.sys.intel
Article #79Re: Undocumented instructions in x86 CPUs
From: John Lauro
Date: Wed, 04 Nov 1992 22:58
Date: Wed, 04 Nov 1992 22:58
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In article <mostert.51@cs.sun.ac.za> mostert@cs.sun.ac.za (A. Mostert) writes: > >Hi all > >I just became aware of an undocumented instruction that (I think) works on >all members of the x86 family. The opcode is D4 10 and it does this: > AH = AL >> 4 > AL = AL & 0xF >Is this a well known instruction ? Does anyone know of any other instructions >(besides LOADALL and the 386 bit string stuff) that Intel did not tell us >about ? > Sure, AAM (ASCII adjust after multiplication) is a well known instruction. They told me (well, not LOADALL but at least AAM) about this one, so I don't know what others they are keeping from you...
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Newsgroups: comp.sys.intel Path: arc1-ca.pugleaf.net!sparky!uunet!caen!acc.flint.umich.edu!jal From: jal@acc.flint.umich.edu (John Lauro) Subject: Re: Undocumented instructions in x86 CPUs Message-ID: <FH==sq#@engin.umich.edu> Date: Wed, 04 Nov 92 17:58:55 EST Organization: University of Michigan - Flint References: <mostert.51@cs.sun.ac.za> Nntp-Posting-Host: acc.flint.umich.edu Lines: 16