[HECnet] RT-11 filesystems, was Re: DECnet-RT?
Mark Pizzolato
Mark at infocomm.com
Tue Mar 31 15:16:22 PDT 2020
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
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