Path: ...!news.nobody.at!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: John Savard Newsgroups: comp.arch Subject: Re: wisdom of the ancients, was Architectural implications of locate mode I/O Date: Wed, 03 Jul 2024 22:17:59 -0600 Organization: A noiseless patient Spider Lines: 28 Message-ID: References: <063ba7a0449d8fe4e7d9966704b907c3@www.novabbs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Thu, 04 Jul 2024 06:18:02 +0200 (CEST) Injection-Info: dont-email.me; posting-host="aa0a3258ec08bcd73a3d2f8b0dd94f09"; logging-data="2752176"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+k1DdVNu2/FwGG+/F2Bg/tomlnwO4sjdo=" Cancel-Lock: sha1:PxoAvh6WffhWXSxCAJzxZjXqNoI= X-Newsreader: Forte Free Agent 3.3/32.846 Bytes: 2338 On Wed, 3 Jul 2024 23:03:24 -0000 (UTC), John Levine wrote: >That is pretty amazing. Did NASA have a plan for reading >those tapes, or did they not realize that normal tape units >need record gaps, or what? It would be interesting to find out the real historical answer to that question. But I can guess at a possible answer. This is before COTS became an acronym. They felt they needed to record those tapes that way, and they figured that reading them should be no big deal, even if existing hardware didn't support it. Another possible approach from the one described (which could potentially lead to errors if data on the tapes was repetitious), would be to connect two computers to the stream of data coming from the tape drive, with them synchronously handing off the responsibility for reading the data back and forth. I'm sure they could have thought of that back then. But they really shouldn't have used standard 9-track tape for this. Something like DECtape, with random-access capabilities, would have been more appropriate. Getting DEC to make a higher-performance DECtape drive with vacuum columns may have been a problem, though. John Savard