Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site intelca.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!mcnc!decvax!decwrl!amd!intelca!cem From: cem@intelca.UUCP (Chuck McManis) Newsgroups: net.arch Subject: Re: Arbitrary byte alignment Message-ID: <420@intelca.UUCP> Date: Fri, 5-Oct-84 19:43:02 EDT Article-I.D.: intelca.420 Posted: Fri Oct 5 19:43:02 1984 Date-Received: Sun, 7-Oct-84 09:11:52 EDT References: <470@houxl.UUCP> Organization: Intel, Santa Clara, Ca. Lines: 26 One of the nicer things the DEC-10s and 20s had was something called a byte pointer. In this context a byte was any arbitrary grouping of bits up to 16 I believe, but it may have gone up to 36, anyway the a string of "bytes" had to start on an 36 bit word boundary but you could have very long strings (ie all of a text file could be considered a string of 7 bit bytes) There were several commands for using bytes notably LDB, DPB for Load from byte pointer and Deposit to byte pointer, both of these opcodes took an accumulator and an effective address of the byte pointer, and transferred the byte to/from the lower (rightmost) bits into/out of memory. It also took care of odd bits, (ie 5 7bit ascii bytes would fit into a 36 bit word with one bit (the lsb) left over) There were also autoincrement and autodecrement modes (this is DEC right ? :-)) and were quite convenient(sp?) for manipulating things smaller than a word. Memory was always accessed as a 36 bit word and the extraction was done in microcode I am pretty sure. I sure wish some of todays processors were so talented and didn't need such archaic things such as byte, and word alignment with bytes fixed at 8 bits. --Chuck -- -- Chuck - - - D I S C L A I M E R - - - {ihnp4,fortune}!dual\ All opinions expressed herein are my {proper,idi}-> !intelca!cem own and not those of my employer, my {ucbvax,hao}!hplabs/ friends, or my avocado plant. :-} ARPAnet : "hplabs!intelca!cem"@Berkeley