Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site sdcsvax.UUCP 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