Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!husc6!cmcl2!rutgers!clyde!cbosgd!cwruecmp!hal!ncoast!allbery From: allbery@ncoast.UUCP (Brandon Allbery) Newsgroups: comp.sys.ibm.pc Subject: Re: SIMTEL20 Message-ID: <3274@ncoast.UUCP> Date: Mon, 20-Jul-87 23:02:42 EDT Article-I.D.: ncoast.3274 Posted: Mon Jul 20 23:02:42 1987 Date-Received: Sat, 25-Jul-87 10:41:42 EDT References: <4UyCLWy00WAKI9k178@andrew.cmu.edu> <881@omepd> Reply-To: allbery@ncoast.UUCP (Brandon Allbery) Followup-To: comp.sys.ibm.pc Organization: Cleveland Public Access UN*X, Cleveland, Oh Lines: 34 Sigh. Nothing like rampant misinformation. The TENEX ftp mode is misnamed; it should be called TOPS, or perhaps PDP-10. The reason is that "TENEX" is not the basic operating system using that particular mode; the problem is a hardware one, not a software one. The basic problem is that the PDP-10 architecture uses 36-bit words rather than 8-bit bytes. IMAGE mode for these machines transmits 36-bit words; TEXT mode probably uses 7-bit ASCII. (36/7 == 5 plus a fraction, resulting in 5 7-bit bytes and one waste bit in a word.) TENEX mode most likely packs 4 8-bit bytes into a word, wasting four bits per word. [I do not know exactly what the setup is; beginning CS students on the PDP-10 I used weren't made privy to network information, and I never got a chance to snarf documentation on all the various data representations beyond RADIX-50 and SIXBIT. Nevertheless, there are obvious arrangements.] The original operating system for the PDP-10 was TOPS-10. Later on, a modified version with extended features (VM paging?) was created; this was TENEX. DEC then made their own version of TENEX; they called it TOPS-20; the TENEX folks, not to be outdone, created TWENEX from TOPS-20. (After which DEC decided to stop producing and supporting the PDP-10. Will UNIX doom the VAX-11 in the same way?) SINTEL20, by its name, runs TOPS-20. Same PDP-10 processor, therefore the same word-to-bit translations apply as do for TENEX. Now, can we kindly cut the TOPS-10/TENEX/TOPS-20 wars and get back to the important stuff? -- [Copyright 1987 Brandon S. Allbery, all rights reserved] [Redistribution permitted only if redistribution is subsequently permitted.] Brandon S. Allbery, moderator of comp.sources.misc and comp.binaries.ibm.pc {{harvard,mit-eddie}!necntc,well!hoptoad,sun!cwruecmp!hal,cbosgd}!ncoast!allbery <>