Sender: eric@ruckus.brouhaha.com From: Eric Smith Newsgroups: alt.folklore.computers Subject: DECtape (was Re: Smallest Storage Capacity Hard Disk?) References: <9su9og$asg@gap.cco.caltech.edu> <9suci1$mhh$1@beta.szi.fh-jena.de> <5s87vtotqkv0h8gs2mkljdnjh5sd66q2tl@4ax.com> <9t3i1l$l31$1@panix2.panix.com> Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy. Date: 16 Nov 2001 22:52:12 -0800 Message-ID: Lines: 19 User-Agent: Gnus/5.0807 (Gnus v5.8.7) Emacs/20.7 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii NNTP-Posting-Host: ruckus.brouhaha.com X-Trace: 16 Nov 2001 22:53:19 -0800, ruckus.brouhaha.com Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!newscore.univie.ac.at!newsfeed.online.be!HSNX.atgi.net!news.kjsl.com!news.spies.com!ruckus.brouhaha.com Xref: chonsp.franklin.ch alt.folklore.computers:94541 johnf@panix.com (John Francis) writes: > (Assuming you are talking about DECtapes) > I think they were three tracks, duplicated. Folklore certainly > suggested that you could, with the appropriate software, recover > data successfully from a DECtape even after burning a hole in it > with a cigarette. I never came across anyone with first-hand > knowledge of this, but heard the story from multiple sources. Mostly right. There were ten tracks total, which were five duplicate pairs. Three of the pairs were for data, one pair for the mark, and one pair for the clock. The mark track stored codes that delineated the block boundaries, end zones, etc. The pairs of heads were wired together in parallel, so there was no way in software to select one head or the other of a pair. The intent was to handle dropouts; if there was a dropout that affected one head, it probably wouldn't get the other, due to the physical arrangement of the tracks. A hole in the tape (if it wasn't *too* big) had the same effect as a dropout.