9 track tapes and block sizes

Chuck Guzis cclist at sydex.com
Thu Sep 17 10:31:58 CDT 2020

On 9/17/20 6:19 AM, Paul Koning via cctalk wrote:

> CDC also supports "long blocks" in which the I/O for a single block is done in pieces, so blocks can be read or written that are longer than what you would think is the limit from the device limits.  I'm not sure how long the longest "long block" is. 

When testing out mods to 1LT, the longest record that I ever
successfully read and wrote was about half a reel at 556 bpi.   Of
course, the data was meaningless.   This was on a Cyber 74 (6600) using
a 657 drive as the target and a derivative of SCOPE 3.1.6 (Special
Systems hack).

Acoustically, the best tapes were the short-record "stranger" tapes.
All sorts of interesting noise.  I could tell from across the room when
someone was running the tape section of the Navy audit tests for COBOL
just by the sounds.


More information about the cctech mailing list