Path: ...!weretis.net!feeder9.news.weretis.net!news.nk.ca!rocksolid2!i2pn2.org!.POSTED!not-for-mail From: mitchalsup@aol.com (MitchAlsup1) Newsgroups: comp.arch Subject: Re: wisdom of the ancients, was Architectural implications of locate mode I/O Date: Thu, 4 Jul 2024 15:04:37 +0000 Organization: Rocksolid Light Message-ID: <6032213dcc3ea9f070dd83b20a655582@www.novabbs.org> References: <063ba7a0449d8fe4e7d9966704b907c3@www.novabbs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: i2pn2.org; logging-data="2139501"; mail-complaints-to="usenet@i2pn2.org"; posting-account="65wTazMNTleAJDh/pRqmKE7ADni/0wesT78+pyiDW8A"; User-Agent: Rocksolid Light X-Rslight-Site: $2y$10$3ezkOphoLvaQETeM13EuMu6ai6r6Zu76autFVyMC9MhJORYd3zIiS X-Spam-Checker-Version: SpamAssassin 4.0.0 X-Rslight-Posting-User: ac58ceb75ea22753186dae54d967fed894c3dce8 Bytes: 2572 Lines: 33 John Levine wrote: > According to MitchAlsup1 : >>S.E.L created a thing they called the RCU (Remote Control Unit). >>It was basically a channel with writable microcode. NASA bought >>a bunch of them because they had tapes from the deep space radio >>telescopes where an entire 9-track tape contained 1 record. NASA >>just started the tape and recorded satellite data until the end >>of the tape, where they would start the next tape just before the >>end of the previous tape. >> >>So we programmed the RCU to read as much as the system memory >>allowed, backed the tap up 1 second while dumping the data to >>disk. Then we started the tape forward with the RCU watching >>the pattern on the tape, when it detected 4096 bytes of the >>last read, it would start streaming data in to memory again. >> >>No other company could demonstrate that they could read one >>of those tapes. >> >>Presto, reading a whole 9-track tape with no inter record gaps !! > > 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? The satellite sending the data just sends a continuous stream from up to 1 light hour away. So the original data had no IRG. It might be the satellites were sending data at the fastest rate the 9-track tapes could write and there was no time to put IRGs on them. {{It has been 40 years since I did some of that}}