[HECnet] RT-11 filesystems, was Re: DECnet-RT?

[Clem cole]

The notch was in the center on the top of the cartridge 

Sent from my PDP-7 Running UNIX V0 expect things to be almost but not quite. 

> On Mar 31, 2020, at 6:16 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
> 
>> On Tuesday, March 31, 2020 at 2:45 PM, Clem Cole wrote:
>> I've forgotten to be honest -- IIRC, no formatting was needed like a traditional tape 
>> drive.   But it is possible we may have had a program to do the formatting and I've 
>> just forgotten it. I do remember that it was a very simple, saturation scheme. We 
>> had a scope on the read electronics of the TA11 and decoded it all.   NRZ style, 
>> 8-bit bytes, no parity, fixed blocks with a prefix and suffix - serial encoding (unlike 
>> a 7/9-track) - which is why the capacity is so low.  Again, I've forgotten, we had 
>> the prints for the TA11 controller and its very possible the format info was in 
>> there -- I really don't remember.   It was just a stream of bits down the tape, not 
>> serpentine like a QIC tape (which has a head that switches 'tracks' and writes a 
>> long stream turns the tape around and then switches to the next head and 
>> writes it backward.   I've forgotten if you got one to two passes on TA11.  
>> Traditional Phillips tape could be flipped over (side 1 and 2).   I don't remember 
>> if TA11's worked that way.
> 
> From what you've described earlier about the special notch in the cartridge, I 
> suspect that the notch only existed on one side so you couldn't actually flip it...
> 
> - Mark