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From: bradley@think.COM (Bradley Kuszmaul)
Newsgroups: comp.unix.wizards,comp.arch
Subject: Re: *Why* do modern machines mostly have 8-bit bytes?
Message-ID: <6724@think.UUCP>
Date: Wed, 22-Jul-87 09:57:45 EDT
Article-I.D.: think.6724
Posted: Wed Jul 22 09:57:45 1987
Date-Received: Fri, 24-Jul-87 04:15:41 EDT
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In article <2807@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>...
>	Anybody for a bit-aligned processor with variable word size (in the
>same way the pdp-10 had variable byte size)?  You could do "ADD X, Y, I"
>where X and Y are the operands and I is the number of bits of precision
>wanted.  I should really mark that with a :-), but I'm partly serious (a
>small part).

The Connection Machine has 64K processors and the instruction set does
include exactly the ADD instruction you describe.  (Except of course, it
is a "vector add").  It can be argued that many applications gain a lot
by not having to do 32 bit operations when the data only has 6 bits of
precision (e.g. vision algorithms).
 -Brad

Bradley C. Kuszmaul, Thinking Machines Corporation, Cambridge, MA
 bradley@think.com
 bradley@think.uucp (i.e. seismo!think!bradley)