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Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!greg
From: greg@sdcsvax.UUCP (Greg Noel)
Newsgroups: net.arch
Subject: Re: Arbitrary byte alignment
Message-ID: <386@sdcsvax.UUCP>
Date: Mon, 22-Oct-84 01:52:18 EDT
Article-I.D.: sdcsvax.386
Posted: Mon Oct 22 01:52:18 1984
Date-Received: Wed, 17-Oct-84 06:20:47 EDT
References: <393@ism780.UUCP>
Organization: NCR Corporation, Torrey Pines
Lines: 19

In article <393@ism780.UUCP> darryl@ism780.UUCP writes:
>Actually, the 1620 addressed its digits in even/odd pairs and, although
>an address had no restriction to be even or odd, there was a performance
>gain by aligning on a pair boundary.  I guess that makes it a decadent
>machine (I know several people who would agree with that estimation).
>	    --Darryl Richman

But I'm one who would disagree......  It was an interesting machine, and
it became my first love.  (Now you know what's wrong with me!)

Actually, even though Darryl is correct that the 1620 fetched in even/odd
pairs, only instruction fetches were optimized to take advantage of this.
(Instructions were twelve digits long and had to be aligined on an even
address.)  Data fetches still fetched each digit individually.  Later in
its evolution, the 1620 Mod II was better at optimizing the references;
it essentially had a (four-digit?) cache, and it could get the second digit
from the same pair in about one-quarter the "normal" access time.
-- 
-- Greg Noel, NCR Torrey Pines       Greg@sdcsvax.UUCP or Greg@nosc.ARPA