Pertec Tape Drive Interface Musings

[Al Kossow]

On 6/10/15 9:12 AM, Mark J. Blair wrote:

> Ok, now three more questions come to mind:
>

> 1) Is it ever acceptable to mix densities on a single tape? I'm not sure that my Kennedy drive will even allow that, but I don't know if that is universal.
>

It happens. Len Shustek's copy of APL/360 has JCL that switches from 1600 to 6250 after the label is written. None of my drives can deal with that, incl the 9610.
I've never tried programatic density switching on the 9610, which is supported.

You also should keep an eye on the rubber capstan, they go gooey. I think I still have a box of capstan motors with the capstans on them from about a dozen drives
I scrapped along with board spares. The 9610 was the only drive I've had luck with recently reading 800bpi tapes. It also is one of the better documented tri-density
streaming drives.

> 2) What's the scoop on a final record overlapping the EOT marker? Or even a new record starting after the EOT marker? I seem to recall reading about some applications that stuck data after the EOT, such as backup volume information.
>

It happens, esp in backup programs. I've seen it a lot in multi-volume DEC10 backups. You have to treat the physical EOT sense tape as a warning.

> 3) Did anybody ever go over to the dark side and implement copy protection on magtapes

Not that I know of.