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From: johnnyw@hubcap.clemson.edu (johnny lee wood)
Newsgroups: comp.sys.m88k
Subject: A question about Mitch Alsup's June 1990 article
Keywords: M88k
Message-ID: <1991Apr19.135732.27609@hubcap.clemson.edu>
Date: 19 Apr 91 13:57:32 GMT
Organization: Clemson University
Lines: 19


In the June 1990 IEEE Micro Mitch Alsup has an article entitled
Motorola's 88000 Family Architecture.  On page 59 he discusses the
floating point multiply pipeline which performs integer and floating point
multiplication.  The first stage multiplies one 32 bit operand by the
low-order 12 bits of the other operand.  The second stage multiplies the
middle-order 10 bits and the third stage the high-order 10 bits.  Then
he states Floating point multiplication continues with .....   This
implies to me that integer multiplication goes to the last stage, which the
multiply and arithmetic unit have in common, after the third stage.

Now for the question.  The MC88100 users manual has a diagram that shows
the integer multiply only going through the second stage of the multiply
pipe and then on to the last stage which the arithmetic and multiply
pipe have in common.  Two stages in the multiply pipe is not enough to
perform the three operations listed above, though.  Any help is greatly
appreciated.

John Wood      johnnyw@hubcap.clemson.edu