Odd PDP-11 tape related question

From: Doc Shipley <doc_at_mdrconsult.com>
Date: Thu Jan 15 02:39:56 2004

On Jan 14, 2004, at 7:51 PM, Johnny Billquist wrote:

> On Wed, 14 Jan 2004 "Fred N. van Kempen" <waltje_at_pdp11.nl> wrote:
>> On Tue, 13 Jan 2004, Zane H. Healy wrote:
>>> Interesting.... BTW, the DDS1 drive I'm using is a DEC TLZ06. Any
>>> idea if
>> Hmm, wasnt the TLZ06 a DDS2 drive? At any rate, yeah, this drive
>> might very well have this "problem" .. I had it with many DDS
>> drives, might even have been a TLZ in that stack... I *do* know
>> I tested it with a TLZ04.

   Sorry to jump in in the middle, but my brane finally dropped into
gear and I remembered that I have the Owner's Manual (EK-TLZ06-OM) for
the drive.

   It's a DDS1 drive. 90M tapes, 2.0GB uncompressed. The first page of
the overview states that it will work with TLZ04 (60M) tapes, as long
as the data on the TLZ04 is not compressed.

> So it might be as some suggested, that the DDS drives aren't too happy.
> I tried with a DDS2 tape in it, if that matters. The system sees the
> drive, and I can mount and dismount tapes, and even eject them.
> Reading or
> writing gives errors, though.

   Most DDS1 drives won't even *load* a 120M DDS2 tape. The TLZ06
almost certainly won't read or write to a 120M tape.

   The manual doesn't even acknowledge the existence of DDS2 or any tape
larger than 90M, probably because they didn't exist when it was
printed. :)

> I have not verified the drive on any other system either, so there are
> several possible problems here, but I thought I'd report what I can
> anyhow.

   First, I'd try a DDS1 tape.

   Also, 4mm drives, by nature of the tape path, are notoriously filthy
around the heads. The tape makes almost a 360 degree turn around a
~1/4-inch capstan, spewing bits of magnetic coating everywhere. A
couple of passes with a cleaning tape often works wonders.

   I could scan this manual if need be. I don't have any OCR software
at present, but I could come up with a creditable imaged pdf.

Received on Thu Jan 15 2004 - 02:39:56 GMT

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