Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: notesfiles - hp internal release 1.2; site hp-dcd.UUCP Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!hplabs!hp-pcd!hp-dcd!donn From: donn@hp-dcd.UUCP Newsgroups: net.unix Subject: Re: RE: tapes as mass storage (sob) Message-ID: <34500001@hp-dcd.UUCP> Date: Mon, 13-Feb-84 16:28:00 EST Article-I.D.: hp-dcd.34500001 Posted: Mon Feb 13 16:28:00 1984 Date-Received: Sat, 11-Feb-84 10:11:53 EST References: <608@druky.UUCP> Organization: Hewlett-Packard - Fort Collins, CO Lines: 16 Nf-ID: #R:druky:-60800:hp-dcd:34500001:000:823 Nf-From: hp-dcd!donn Feb 7 13:28:00 1984 I tried (under duress) using a 7 track as a disc, but it didn't work. The problem was the well known "crap in the gap" problem. SOME tape drives are accurate enough that they don't generate crap in the gap, and SOME are tolerant enough to skip over the crap, but don't count on it. DecTapes have a "clock track" that is written "once" and used to clock the bits onto the tape so that physical block length doesn't vary from write to write. The clock on 7 track tape is taken from the OR of the 7 bits so if the capstan slips a bit, so do the bits. Did you ever try taking moving one of those tapes from one drive to another; not really likely to work. Forget about ever getting a CDC 6400 (at least early '70s vintage) to read such a tape; they had a real problem with crap in the gap. Donn Terry hplabs!hp-dcd!donn