[TUHS] Fwd: Choice of Tape Format for BTL UNIX Distro

[Peter Yardley via TUHS]

Thanks I’ll try sending this to the list.

> Begin forwarded message:
> 
> From: arnold at skeeve.com
> Subject: Re: [TUHS] Choice of Tape Format for BTL UNIX Distro
> Date: 1 April 2026 at 8:41:04 pm AEDT
> To: peter.martin.yardley at gmail.com, arnold at skeeve.com
> 
> I don't see the list in the To: or CC:
> 
> Thanks for confirming my memory that 6400 BPI drives existed.
> 
> Peter Yardley <peter.martin.yardley at gmail.com> wrote:
> 
>> Don’t know if this will hit the list.
>> 
>> My memory is we had a 1600 BPI tape drive. Of course that would have read 800BPi tapes.
>> 
>> The 6400 BPI drives were much more expensive so not everyone had one.
>> 
>>> On 1 Apr 2026, at 7:51 pm, Arnold Robbins via TUHS <tuhs at tuhs.org> wrote:
>>> 
>>> In that time frame, 800 BPI was pretty standard. 9 tracks gave you
>>> eight bits of data plus a parity bit.
>>> 
>>> By the mid-80s, 1600 BPI was pretty common for the same media, so
>>> the BSD distributions might have been 1600 BPI tapes.
>>> 
>>> I think at some point 9 track tape drives hit something like 6400 BPI,
>>> but I may be hallucinating the memory.
>>> 
>>> HTH,
>>> 
>>> Arnold
>>> 
>>> segaloco via TUHS <tuhs at tuhs.org> wrote:
>>> 
>>>> Surprise surprise, another hyper-specific topic incoming.  I am curious
>>>> if anyone on-list can provide insight on this topic.  Setting Up Unix -
>>>> Seventh Edition indicates:
>>>> 
>>>>> The tape is 9-track 800 BPI...
>>>> 
>>>> Was this a matter of convention given the general computing ecosystem at
>>>> the time, or was this more driven by Bell System standards for magtape?
>>>> 
>>>> I find myself curious as I recently procured a 7-track 556 BPI transport
>>>> which, while not applicable to V7 UNIX tapes as so described, has me
>>>> itching to explore the world of magtape further, including eventually
>>>> tracking down a 9-track supporting the necessary BPI should another UNIX
>>>> tape needing preservation surface.
>>>> 
>>>> I also recently got a QIC drive (not the right size for the early 90s
>>>> BTL tapes I have) and am exploring repurposing the read head to yank
>>>> data off these janky QIC tapes I have.  Needless to say, magnetic tape
>>>> media and preservation is on the mind lately.
>>>> 
>>>> Further on the subject of UNIX tapes though, was there any regular
>>>> shipment of other media not matching this description or was it pretty
>>>> settled that
>>>> 
>>>> order_unix()
>>>> 
>>>> has a return type of
>>>> 
>>>> mt_track_9_bpi_800_t
>>>> 
>>>> ?
>>>> 
>>>> - Matt G.
>> 
>> 
>> .1.3.6.1.4.1.8852.4.2
>> Peter Yardley
>> peter.martin.yardley at gmail.com


.1.3.6.1.4.1.8852.4.2
Peter Yardley
peter.martin.yardley at gmail.com