Re: Old Magnetic Tapes

From: Bill Gunshannon (bill_at_gw5.cs.uofs.edu)
Date: 12/17/03 

Date: 17 Dec 2003 14:06:17 GMT

In article <3fe05d40$0$4741$61fed72c@news.rcn.com>,
        jmfbahciv@aol.com writes:
> In article <brplnu$64cah$1@ID-135708.news.uni-berlin.de>,
> bill@gw5.cs.uofs.edu (Bill Gunshannon) wrote:
>>In article <broquh113re@enews4.newsguy.com>,
>> healyzh@aracnet.com writes:
>>> David J. Dachtera <djesys.nospam@neoasrptahmlnionwk.net> wrote:
>>>> The density may turn out to be the biggest challenge. Could be 800BPI,
>>>
>>> How common was it to write 800BPI tapes on DEC HW, especially in the
>>> mid-to-late 80's? I've got a customer that wants me to retrieve some
> data
>>> off a bunch of 9-Tracks once I verify our drive works. Our drive only
>>> supports 1600/6250.
>>
>>I would suspect that any taqpe old enough to have been written at
>>800BPI is likely to be unreadable by this point in time anyway.
>
> why?

Because magnetism isn't permanent. Over time just passing thru the
earths own magnetic field weakens the field. Add into that the fact
that each layer of tape is immediately next to the previous and
following layer and these magnetic fields also interact over time.
And, as was already mentioned, the oxide itself becomes unstable
over time. I have had tapes stick together and have had tapes that
shed their oxide when attempts were made to read them after a long
wait. How long ago did 800BPI stop being the standard? :-)

As a side note, if someone closer isn't found, I do have PDP-11's
here with tape drives on them. Assuming the tapes are readable
I could probably extract the data or maybe even copy them to
container files that could be used with something like SIMH.

bill 

-- 
Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
bill@cs.scranton.edu     |  and a sheep voting on what's for dinner.
University of Scranton   |
Scranton, Pennsylvania   |         #include <std.disclaimer.h>

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