Your Mother Saves Data on EightTrack Tapes

No, not that kind of eight-track tape.

This is a reference to one of the latest manuals to hit Al Kossow's site.

The seven-track tapes used with IBM mainframe computers recorded the parity bit, and then the remaining data bits, across the width of the tape in normal order.

Nine-track tapes, for some reason, re-ordered the data bits on the tape. It is unclear, to me, at any rate, what possible benefit that could have provided, since an error is an error, no matter in which bits it occurs; whether the two bits are adjacent or not seems to have no importance.

But the NTDS used an eight-track magnetic tape, which also had a bit, and one timing track. The timing track doesn't seem to have allowed the tape to perform the kind of sophisticated functions buttociated with DECtape or LINCtape, but obviously it could have simplified reading the tape in a normal fashion as well, especially when it is recorded with NRZI rather than PE. (A timing track would be a way of allowing 3200 bpi recording during the time of 1600 bpi technology, therefore.)

John Savard