HP 85 & a bit more.

A couple of points: On the almost nothing they have in common... Physically, they don't, and they don't really have much in common in terms of the tracks on the tape. But they've got a unique feature in common. They are used in a way that are block addressable, like a disk. In fact Thompson's first UNIX on the PDP-7 used the original DECtape as it's primary storage. On the use of DECtape IIs for the HP-85 and 9800 series... Please don't. As much as I love my HPs, I desperately keep any DECtape IIs I have for use with DEC stuff. The DECtape IIs are formatted at the factory and I know of no way to format them with controllers in the field. (I'd love to be proved wrong about that, BTW.) So I (and I'm sure others) would be grateful if DECtape IIs could be saved for use with TU-58s.