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hckr83



Joined: 12 Nov 2006
Posts: 86
Location: usa
hckr83
I am working on an emulator and need to know what should be done when repne prefix is there and the string instruction is movsb..is it just ignored and acted like rep? or invalid opcode?

now I know most assemblers will warn against this, but at the bytelevel anything is possible..

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x86 CPU Emulation library: http://sourceforge.net/projects/x86lib
Post 25 Feb 2007, 01:16
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
why not just try it? Wink
Post 25 Feb 2007, 07:07
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MazeGen



Joined: 06 Oct 2003
Posts: 975
Location: Czechoslovakia
MazeGen
I guess it is the same like with 0xF3 prefix - if the repeated instruction doesn't alter ZF, it is REP prefix, otherwise it is REPE/REPZ.
Post 26 Feb 2007, 10:06
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Vasilev Vjacheslav



Joined: 11 Aug 2004
Posts: 392
Vasilev Vjacheslav
check intel instruction set
Post 26 Feb 2007, 11:21
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MazeGen



Joined: 06 Oct 2003
Posts: 975
Location: Czechoslovakia
MazeGen
According to oficial documentation, instructions like REPNE MOVSB or REPNE STOSB actually do not exist. And I found nothing related to their behaviour.
Post 26 Feb 2007, 11:39
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