10 Mar
2002
10 Mar
'02
1:57 p.m.
Geoff Roberts wrote:
Could it be
that the TK50 tape doesn't play well with the TQK70
controller? Would it be better if I hooked the TK50 to the DEBNT,
but where on the backplane rear do I connect this sort of thing
and how is the IDC connector wired on the VAXBI side?
The TK70 will read TK50
carts. It will not write to a previously used TK50
unless it is bulk erased, and I
wouldn't trust it then. It's meant to write only to TK70 media.
I don't think the TK50 will work properly (or at all) on a TQK70 controller. From all the information I have ever been able to find,
there are only
three differences between unused TK50 media and unused TK70 media:
(a) One is CompacTape other is CompacTapeII
(b) CompacTape letters are brown, CompacTapeII letters are blue
(c) Cost
Memorex used to have a site on DLT tapes. Physical properties
were identical for the media.
While I do have an occasional problem with a TK70 drive,
every time a head cleaning has cleared the problem.
Degausing a tape used in either a TK50 drive or a TK70 drive
should be done before switching to the other drive.
The TK70 controller was often used to "FIX" problems with
TK50 drives. All of the TK50 drives I have ever used work
much better with the TK70 controller - of course, a TK70
drive works even better.
All of my experience with the TK50 and TK70 drives has
been with RT-11 on a PDP-11 (obviously).
You'd be far better off getting a TK70 tape for
it.
Cheers
Geoff in Oz
I have never had that problem. Bad tapes I have had, but then
in most cases, they would not work well with a TK50 either.
And since the speed of the TK50 is so slow compared to the
TK70, I don't think I ever managed to verify if a TK50
wrote the correct information in the first place except during
testing with a small number of small files. The first time I
wrote a full 32 MBytes with a TK50, I quit after the
"/VERIFY:ONLY" command had run for an hour and was still
not finished. With a TK70, both the write and verify times
are about 7 minutes for 32 MBytes on a PDP-11. Since
it takes about 5 minutes to compare two 32 MByte files
on an RD53 under RT-11, the 7 minutes time is excellent.
Of course, on my "newer" PC that now takes about 2 SECONDS
when I run RT-11 and compare two 32 MBytes "devices".
Sincerely yours,
Jerome Fine