A little HP9877 info

From: joe <rigdonj_at_intellistar.net>
Date: Fri Jun 29 16:48:27 2001

At 08:55 AM 6/29/01 -0700, Frank wrote:
>ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
> > If the 9815 encoding is idential physically the 9825 one (that is to say,
> > a 9815 tape read at the 9825 speed contains the data encoded as above
> > with the same frequencies as the 9825 uses) then the 9877 can read it. If
> > not, then IMHO it can't. And since the 9815 and 9825 tape controllers are
> > very diferent, I think it's unlikely that the 9877 (which uses a
> > controller that's essentially the same as the 9825 one) can handle 9815
> > tapes. Pity.
>
>Here's a snippet from _Mid-Range Calculator Delivers More Power
>at Lower Cost_, by Douglas M. Clifford, F. Timothy Hickenlooper,
>and A. Craig Mortensen, in the June 1976 HP Journal:
>
>"...It was determined that a level of performance below that of the
>9825A Calculator (see article, page 2) would be adequate, so the
>search speed was reduced to 60 ips and the read/write speed to 10 ips.
>The recording density was set at 500 bits per inch. Because of these
>reduced demands all of the encoding and decoding of the bits can be
>done in firmware. Also, a frequency-lock control loop is used for the
>motor control instead of a more costly dc servo (more about this
>later)."
>
>Does that give you any clues? Unfortunately I don't think it says
>anything about the recording density of the 9825 tapes.


     FWIW there's a big article in one of the older HP Journals about the
tape drive. The article is part of a larger article about one the terminals
that used that drive. (I think it was the first HP device to use this type
drive.) There may also be details about the drive in the later HP Journal
that contained the numerous articles about the 9825. Sorry I don't
remember the dates of the two Journals and I don't have time to look them
up right now.

      Joe


>-Frank McConnell
Received on Fri Jun 29 2001 - 16:48:27 BST