Reading old HP-65 program cards

[Gene Dorr]

Re: visual decoding of the card -- I actually wondered about that for a while, as I too remember the discussion. In fact, there's a decent image of the magnetic recording on those cards on page 7 of the November 1976 HP Journal, in an article about the HP-67. But I am extremely skeptical that it could be decoded visually -- according to Bob Taggart, the density is around 300 bits per inch.

Plus, I don't recall anyone reporting (and documenting) the format of the data tracks recorded by the HP-65. I'd love to be wrong about that, though.

I have had issues reading old HP-71B magnetic cards, so I am concerned about even older HP-65 cards. They might be less of a problem though, since the HP-65 card reader was motorized, and so read/write speed would be less variable.