Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!bionet!agate!usenet
From: web@garnet.berkeley.edu (William Baxter)
Newsgroups: comp.sys.intel
Subject: Re: Undoc'd immediate MUL in 80X86 (incl.8086)
Message-ID: <1990Feb14.234128.17866@agate.berkeley.edu>
Date: 14 Feb 90 23:41:28 GMT
References: <622@tuura.UUCP>
Sender: usenet@agate.berkeley.edu (USENET Administrator;;;;ZU44)
Reply-To: web@garnet.berkeley.edu (William Baxter)
Distribution: comp
Organization: UCB Math Dept
Lines: 15
In-reply-to: risto@tuura.UUCP (Risto Lankinen)

In article <622@tuura.UUCP>, risto@tuura (Risto Lankinen) writes:
>A little experimenting with Microsoft Macro Assembler version 5.10 and
>the instructions AAM and AAD revealed a neat way to do immediate 8-bit
>MUL and DIV on 80X86:s.  The 'feature' is *ABSOLUTELY* undocumented by
>either Intel or Microsoft or any other organization associated.  

This quirk is documented and supported by Eric Isaacson in his shareware
assembler A86. (available on Simtel20)  He claims that modifying the
immediate operand to AAD has no effect on NEC V20 and V30 chips, as it is
assumed to be 0Ah.

William Baxter

ARPA: web@{garnet,brahms,math}.Berkeley.EDU   
UUCP: {sun,dual,decwrl,decvax,hplabs,...}!ucbvax!garnet!web