Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!rpi!uupsi!ccavax!bruce
From: bruce@ccavax.camb.com
Newsgroups: comp.sys.dec
Subject: Re: various tape capacities
Message-ID: <31808.26e4f416@ccavax.camb.com>
Date: 5 Sep 90 16:48:21 GMT
References: <1806@gazette.bcm.tmc.edu> <6491@tekgen.BV.TEK.COM> <6215@hub.ucsb.edu>
Organization: Cambridge Computer Associates, Inc.
Lines: 19

In article <6215@hub.ucsb.edu>, hbo@sbphy.ucsb.edu..ucsb.edu (Howard B Owen) writes:
>    I vaguely recall someone claiming that TK50 cartridges could be used
> at TK70 densities if only a certain magic sequence were followed. Given
> the difference in cost between TK70 carts from DEC and TK50s from 3M,
> using the latter could result in substantial savings. Does anyone know

The TK50 and TK70 tapes are similar, BUT to write one format on a tape
already in the other format requires the tape being bulk erased first.
Bulk erased or virgin tape can be used in either drive. 

The TK70 tolerances and tighter, and the tape it self may be different
(not sure), but I think DEC is now only making the TK70 grade stuff. S/W
distribution from DEC will always be in TK50 format, but may be on
the better media.

Just wait though! We are probably going to get yet another member to the family 
that will only be able to read the TK50 and TK70 tapes, but will be able
to write its own type. I assume it will be even tighter tolerences, but
maybe the coating formulation changes too.