On 09/30/2017 10:31 PM, Chuck Guzis via cctalk wrote:
On 09/30/2017 06:29 PM, Jon Elson wrote:
Ahh, but the genius is built into the heads! Note that nobody
recorded 800 BPI on 7-track tapes. I think they supported 200 and 556
BPI, only. There were some low-density 9-track tapes, but generally
most 9-tk tapes were 800 BPI.
Say what? We certainly did a lot of tape at CDC at 800 NRZI on the
607s.657 and 667. Most IBM 729s, but for the very early models could
support 800 NRZI.
800 NRZI for 9 track was common only until about 1970; 1600 PE was
available on the 2400 series. By 1975, it had pretty much become the 9
track interchange standard. In spite of packing more data on a piece of
tape, 1600 PE is actually more reliable than 800, as a dropped bit
transition doesn't corrupt data downstream.
OK, I never used 7 track tapes, but I thought that they were
recorded at lower density than 9 track.
Yes, I know about 1600 PE, 3200 PE and 6250 GCR.
Jon
