6 Feb
2006
6 Feb
'06
7:47 a.m.
At 06:59 PM 2/5/06 +0000, Tony wrote:
No, the drives and tapes used on the 9830, 9865, and the other 98x0
machines is an earlier tape and it's different. They're more like audio
tapes and have an all plastic shell and the tape is driven via the hubs.
The tapes that I was talking about are similar to the HP-85 tapes but much
larger (DC-600 size) and use an aluminium base plate and are used in the HP
9142, 9144 and 7942 and similar drives. FWIW some of these larger tapes are
marked 16 track and others are 32 track but they both look alike.
big DC-600
type tapes used in the HP 9144, etc. They did use a different
tape in some earlier products but they were VERY different and immediately
recognizable. I have a couple of those drives but I've never seen a tape
for them. It was driven like an audio cassette tape via the hubs.
If that's the tape I'm thinking of, it's used in the 9830, and I think
also the 982. There was an external tape drive for these machines that I
forget the number of (HP9865???)
The tapes are mechanically compatible with audio compact cassettes, but the
tape is almost certainly different. These drives detect the clear leader
by an optical sensor that reflects off the inside of the cassette shell
where you'd expect the capstan/pinch roller to be, you need to use a
light-coloured cassette. I've got a few Verbatim digital cassettes that
work fine in my 9830.
That's good to know. I have a 9830 and a 9865 but I've never tried to
use the tape drives in them.
Interesting thing : That drive is mechanically very similar to the one in
a Racal Thermionic Digideck. Similar enough that some parts will
interchange. And the encoding scheme -- a pulse on one track for a '1', a
pulse on the other track for a '0' and a pulse on both tracks for a
marker (in the case of the HP, it's a byte marker) is the same too. As is
the dact that the thing records 9 bits for each byte, the middle bit is
some kind of marker to distinuish headers from data (the advantage of
making it the middle bit is that you can read it with the tape moving in
either direction.
I would guess that the mechanism is not wholely an HP design/build...
Probably not. I don't really know anything about those older drives but
I know that the HP Journal said that the later drives (HP-85 style) was a
joint program bewteen HP and 3M so I'm assuming that onr or the other (or
both of them) designed it.
Joe
-tony