On 01/18/2016 09:46 AM, Jon Elson wrote:>
Longevity of tapes was very spotty. Some expensive, name-brand tapes just disintegrated after a few years. Others have held up amazingly well. Last year I read in some 1993 backups of my MicroVAX system with no trouble at all. I did have to clean the tape head after every tape, but that wasn't greatly different from when the tapes were new.
I've not noticed that the 3M 700-series "Black Watch" tapes were any better or worse than other tapes of the time--if anything, they seem to stick less. AFAIK, the back-coating on the 700 series was mostly a matter of texture, not an applied substance.
There were, however, some terrible tapes. Scotch brand 8104 tapes are among the nastiest. The tape binder often bleeds through the oxide face of the tape. You can't even get the things through a cleaning machine without having it jam--even after several passes (the silicon carbide blade is scary-sharp, and the damned tape will even stick to that.) I've found that coating is the only way to get those tapes to make their way through a tape drive without halting.
Memorex tapes from the 80s (MRX IV and V) can be pretty lousy on their own and Memorex sold buckets of them cheaply. Baking is pretty much mandatory.
Strangely, a crappy tape from a manufacturer doesn't mean that the same outfit's floppy disks are just as bad. Wabash-branded tape is actually pretty decent, while Wabash-branded floppy disks are the devil's own spawn. Go figure.
--Chuck
