Newsgroups: comp.arch
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Bitfield instructions--a good idea?
Message-ID: <1991Apr18.195841.10588@zoo.toronto.edu>
Date: Thu, 18 Apr 1991 19:58:41 GMT
References: <1991Apr15.193425.3436@waikato.ac.nz> <1991Apr18.093804.18183@odin.diku.dk>
Organization: U of Toronto Zoology

In article <1991Apr18.093804.18183@odin.diku.dk> torbenm@diku.dk (Torben [gidius Mogensen) writes:
>A ZIP instructions takes two words abcde..., ABCDE... and merges the
>bits into a double word aAbBcCdDeE... (or two half words into a word)
>An UNZIP instruction is the inverse of ZIP...

Unless access to memory is seriously expensive, table lookup can implement
both of these operations quite efficiently.  Agreed, it's not as fast as
having them wired in...
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry