Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!bbn.com!mips2!granite!kittlitz
From: kittlitz@granite.cr.bull.com (Edward N. Kittlitz)
Newsgroups: comp.unix.sysv386
Subject: Re: How to get past end of cpio archive on tape
Keywords: eof
Message-ID: <1991Jan4.134833.11362@granite.cr.bull.com>
Date: 4 Jan 91 13:48:33 GMT
References: <1990Dec12.050414.15575@bjm.wimsey.bc.ca> <1162@bcs800.UUCP> <301@bria.AIX> <1023@mwtech.UUCP> <568@fciva.FRANKLIN.COM>
Organization: Bull HN Information Systems Inc.
Lines: 24

Cartridge tapes are recorded in "serpentine" format. I believe a 150MB
tape has 18 tracks. You can think of it as
	1->1->1->.....1->
	2<-2<-2<-....<-<2
	3->3->3->.....3-> etc.
(although it isn't actually in that order).  I am no peripherals expert,
but it seems to me that there are several advantages:
- as recording heads (tracks) get thinner, you get more on the
  same length of tape. Of course you probably need to make
  the tape with a better magnetic coating, but you aren't doing
  the audio cassette trick of thinner tape (am I correct here?) to
  get more info into the same physical cartridge container.
- it should be easier to keep the tape streaming, because a track is
  only 1 bit wide.

From my reading of the Wangtek 5150 and Archive 2150 manuals, the erase
head is full width. I don't know if there are actually 18 
"tips" on a fixed head for recording/sensing, or whether the record/sense
head moves up and down. I have a suspicion it is the latter, as I have
watched an internal cart-tape drive move a head assembly across the
width of the tape during tape load.
-----
E. N. Kittlitz		kittlitz@granite.cr.bull.com
Contracting at Bull, but not alleging any representation of their philosophy.