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From: jesup@pawl18.pawl.rpi.edu (Randell E. Jesup)
Newsgroups: comp.arch
Subject: Re: Prefix instructions (Was: RPM-40 microprocessor; data from ISSCC)
Message-ID: <448@imagine.PAWL.RPI.EDU>
Date: 29 Feb 88 11:37:21 GMT
References: <9651@steinmetz.steinmetz.UUCP> <9678@steinmetz.steinmetz.UUCP> <1199@microsoft.UUCP>
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In article <1199@microsoft.UUCP> ccplumb@watmath (Colin Plumb) writes:
>The only funny question is the semantics: what does a prefix do to an
>instruction without an immediate constant?

In the RPM-40, nothing.  Goes to the great bit-bucket in the sky.
In the more general case you mentioned, you COULD seperate prefixes from their
instructions, but it would really make the reorganizer hard to write (I
know, I've written them!)  Also, the prefix logic would be more
complicated (and thus slower/bigger).

     //	Randell Jesup			      Lunge Software Development
    //	Dedicated Amiga Programmer            13 Frear Ave, Troy, NY 12180
 \\//	beowulf!lunge!jesup@steinmetz.UUCP    (518) 272-2942
  \/    (uunet!steinmetz!beowulf!lunge!jesup) BIX: rjesup

(-: The Few, The Proud, The Architects of the RPM40 40MIPS CMOS Micro :-)