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From: kev@hpcpbla.HP.COM (Kevin Jones)
Newsgroups: comp.periphs
Subject: Re: Cartridge tape questions
Message-ID: <1450002@hpcpbla.HP.COM>
Date: 30 Oct 89 08:20:36 GMT
References: <169@iquery.UUCP>
Organization: HP Computer Peripherals Bristol, UK
Lines: 34

What tends to happen with quarter inch tapes is that to get more data 
onto a tape, successive standards define more tracks on the tape.

As the number of tracks on a tape increase, their width decreases
(after all, its still 1/4 inch  :-)

When it comes to writing a track, the WIDTH of the write head which 
creates the track is (approx) the width of the track. 

Higher capacity drives therefore have narrower write heads than the older
drives (QIC24 -> QIC150 -> QIC320 etc....). 

This means that it is impossible for a "newer" drive to write "wide tracks"
(which the "older" drives can read).                               

It IS possible however for a "newer" drive to READ tapes written with 
wider tracks since the read head fits "inside" tracks (as written by either 
drive). 

It is therefore possible to build a drive which reads/writes a new format 
but can only read older formats. 

It is extreemly difficult (read also: expensive) to try and build a drive 
to read and write all formats. 


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Kevin Jones.                       | Hewlett Packard Ltd,
                                   | Computer Peripherals Bristol,
kev%hpcpbla@hplb.hpl.hp.com        | Filton Road,
                                   | Stoke Gifford,
Tel: 011 44 272 799910 (ext 22351) | Bristol.   BS12 6QZ.
                                   | ENGLAND.
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