🚀 go-pugleaf

In article <20@lemans.dec.com> allen@det.dec.com writes:
>I've been using 4mm for a few months, this is what I have found:
.......>
>  - it is an EXCHANGE medium.  I know of more than 1 site that can not
>    read 8mm tapes written on a different machine.  E.g. can not
>    read a tape written on a Sun on a DECstation.
-----
(i guess we're pushing a year on our 8mm's)
 We have had no problem reading 8mm tapes brought to our VAXstations
(running VMS) with TTI controllers from diverse sources:
  other VAXes with other controller brands, 
  SUNs with who-knows-what (from Saskatoon)
  various beasties at Berkeley.

althought by no means exhaustive ("i've never seen an 8mm tape i couldn't
 read"), it's at least as good as my 20-years of experience in reading 9-track
tapes from multiple suppliers.
Why a DECstation cannot read a SUN tape?  Since i plan to put 8mm
on my DECstation someday, i'd love to know...

>
>  - I have been told that an 8mm tape has a limited number of hours
>    of life, partly because it gets wrapped 270 degrees around the
>    heads.  The 4mm was much less.  Is  there an engineer in the house?
yes, but not a magtape engineer.
we've got users who have read and reread and rewound and reread their
little tapes many many times.  i've seen them wear out 9 tracks.
so far (knock on small shoeboxes) no in-use tape has drifted above
 0.20% ECC recovery (the TTI system has those numeric readouts --
 so far we've seen only two bad (>0.50% retry) tapes out of about 100.
and those were when they were new.
i've torn the drive apart to extract a tape once (i was pushing the
emergency release too gently to trigger it) when a drive's motor
burned out (actually, when some 12volt-handling part stopped handling).
and during acquisition inspection i had one apart while running.
they're pretty gentle in their tape handling.  when they go into
rewind they loosen from the spinning heads to lower wear.
i agree -- a 90 degree wrap will be gentler, but must also require
a more severe tracking angle for the head to wipe the full width of
the tape.  as long as they hold the tape away from the spinning sawblade,
(2-inch videotape drives use vacuum to hold the tape back from the heads)
that won't increase wear.

8mm serves us very well today.  We could use the fast seek of 4mm.
Based on prices, usage, etc., i expect we'll swing to 4mm in about
18 months.  Unless the 8mm's are still working so well.
(but then, we just retired the 7-track tape from our 11/780)
--dick