9 track tapes and block sizes

jim stephens jwsmail at jwsss.com
Sun Oct 4 22:58:19 CDT 2020

On 10/4/2020 8:47 PM, Chuck Guzis via cctalk wrote:
> On 10/4/20 8:12 PM, jim stephens via cctalk wrote:
>> On 10/4/2020 4:00 PM, Chuck Guzis via cctalk wrote:
>>> On 10/4/20 1:50 PM, J. David Bryan via cctalk wrote:
>>>> <snip>
>>> I don't believe that you're missing anything.   When I process these
>>> files, I mask off the lower 24 bits as the block length.  A 16MB tape
>>> block is impossibly large in any case.
>>> --Chuck
>> Oil logging tapes write 9 tracks with no inter record gaps or file marks
>> till EOT.  I'm guessing you've not digitized any of those?
> A couple of years ago, one of the NASA logging units turned up for not
> much money.  Big flight case.  Basically consisted of a Kennedy
> incremental drive (i.e. stepper) brought out to several BNC connectors.
> My recollection is that the Kennedy 9000-series unit was NRZI and likely
> 800 bpi.   Unlikely that you could get 16MB on a 10.5" reel with that.
> Probably unreadable on standard tape drives with limited formatter
> memory.  I've also mentioned CDC 7-track "long tapes".
> I've certainly seen the 9-track analog telemetry tapes also, but they're
> a much different kettle of fish.
> --Chuck
The Microdata 1600 with the NRZI interface could write an entire tape of 
normal "record" data  with a Pertec drive.  We wrote code to write IBM 
records on our system and make our 360 happy.  One of the debug efforts 
had a bug in some experimental code that neglected to do the eot order 
to the controller, and the entire tape was one record.

The system did retries on it till the system crashed, then sucked the 
entire tape into the vacuum columns.  We weren't popular that day.

The system I mentioned earlier was at company my partners worked at 

I had not seen your earlier no tape gap mentions.


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