Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!well!mingo
From: mingo@well.sf.ca.us (Charles Hawkins Mingo)
Newsgroups: comp.sys.mac.misc
Subject: Re: DAT backup for MAC?
Message-ID: <23205@well.sf.ca.us>
Date: 17 Feb 91 22:57:02 GMT
References: <789@david.UUCP> <23192@well.sf.ca.us> <10851@jarthur.Claremont.EDU>
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 35

In article <10851@jarthur.Claremont.EDU> epan@jarthur.Claremont.EDU (Eric C. Pan) writes:
>
>	Charlie Mingo talked in his post about unusability of audio DATs for 
>computer backup due to the lack of control.  But what about Sony's 
>L-control(?), S-control(?) and Pioneer's control system. A lot of companies 
>produce components that had control interfaces intended for control by a 
>reciever/pre-amp.  Are those usable from a computer-control standpoint?

	Well, I'm no expert on the specifics of L-Control, S-Control, et al.,
but the reciever/pre-amp coordination system are usually only designed to
do simple things like "start PLAY" or "REWind", not "advance to frame
08A3F1 and transmit the next sixty frames."  A computer controller requires
extremely precise control over the device, so that specific locations can
be reliably accessed.  It also usually needs some sort of error detection/
correction system, which audio DATs generally lack.  (Audio DAT's have
mechanisms to make errors less noticable, such as interpolation, but data
DAT's have to eliminate errors completely.)  And consumer DAT's *do* produce
a lot of errors of the bit level.  According to reports on the dat-heads
mailing list, 2500 errors/second is not unheard of.  This is not a problem
for recording *music*, but data would be really corrupted by this.  (The
best DAT's have around 100 errors/second.)

>p.s. I believe the 10mg/tape capacity Charlie quoted is based on hardware
>compression and not the "real" or "raw" storage capacity of DAT tapes.

	Well, that was 10GB (GigaBytes), and there surely is some compression
involved, but I've never seen a DAT data cassette system which offered less
than 2GB.  Remember that the PCM system involves around 1.5 million bits/
second of recording time, which suggests a "raw" data storage of 1.35GB
on a 120min cassette.
-- 
______________________________________________________________________________
Charlie Mingo					Internet: mingo@well.sf.ca.us 
2209 Washington Circle #2				  mingo@cup.portal.com
Washington, DC  20037	    CI$: 71340,2152	AT&T:  202/785-2089