PDP-11 tape question

Chuck Guzis cclist at sydex.com
Tue Jun 23 20:57:20 CDT 2020

I've been processing some PDP-11 9 track (800 NRZI) tapes and run across
something that I don't recognize.

Every file on the tape consists of a number of 512 byte blocks (okay,
that's normal) but at the head of each file, there's a short block of 14

Usually, a short record like this is discarded as "noise" on many
mainframe tape systems, but here it's consistently present. Here's what
one of the records looks like:

15 34 fe 51 fe 76 01 01 00 00 01 80 10 00

Doesn't seem like a file name in RAD50 format, so I'm puzzled.

Inquiring minds want to know...


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