Re: Undocumented instructions in x86 CPUs

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Article #878

#878

From: Michael R Castle
Date: Thu, 05 Nov 1992 10:17

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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 ?

hmm.... listed in my Microprocessors and Peripheral Handbook... AAM 

Also, 
AAA   37
AAS   3F
AAD   D5 10

maybe you just need better documentation   :-> 

mrc

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From: mcastle@mcs213d.cs.umr.edu (Michael R Castle)
Subject: Re: Undocumented instructions in x86 CPUs
References: <mostert.51@cs.sun.ac.za>
Date: Thu, 5 Nov 1992 10:17:17 GMT
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