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From: herrickd@iccgcc.decnet.ab.com
Newsgroups: comp.arch
Subject: Re: new instructions
Message-ID: <4780.284b79e4@iccgcc.decnet.ab.com>
Date: 4 Jun 91 16:30:44 GMT
References: <12947@mentor.cc.purdue.edu> <182@armltd.uucp>
Distribution: comp
Lines: 21

In article <182@armltd.uucp>, abaum (Allen Baum) writes:
> In article <12947@mentor.cc.purdue.edu> hrubin@pop.stat.purdue.edu (Herman Rubin) writes:
> 
[much omitted throughout the quotations]
>>This points out another reason for cheap instructions at little cost.  
>>
>>Now how much additional silicon would it take to provide both signed
>>and unsigned?  
> 
> Do not presume that because
> unsigned & signed multiply are both multiplies, that including both
> is cheap. It may not be the case. Boothe style mults. are implicitly
> signed, for example. To pretend they aren't mean multiplying two
> 33 bit numbers.

What fantastic advantage does one derive from using "Boothe style mults."
that makes up for losing unsigned arithmetic.  This sounds to me like the
reason for not using them in a general purpose computer.

dan herrick
herrickd@iccgcc.decnet.ab.com