Undocumented instructions in x86 CPUs

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Article #73

#73

From: A. Mostert
Date: Wed, 04 Nov 1992 10:36

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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 ?

    
A. Mostert
Stellenbosch, RSA
mostert@cs.sun.ac.za

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Path: arc1-ca.pugleaf.net!sparky!uunet!ogicse!psgrain!ee.und.ac.za!shrike.und.ac.za!hippo!beldin.sun.ac.za!mostert
From: mostert@cs.sun.ac.za (A. Mostert)
Newsgroups: comp.sys.intel
Subject: Undocumented instructions in x86 CPUs
Message-ID: <mostert.51@cs.sun.ac.za>
Date: 4 Nov 92 10:36:13 GMT
Article-I.D.: cs.mostert.51
Sender: news@hippo.ru.ac.za
Organization: University of Stellenbosch
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