[TUHS] Choice of Tape Format for BTL UNIX Distro

[Peter Yardley via TUHS]

Thanks Clem

My submissions to the list were getting lost. 

Been about 30 years since I last used tape in anger. Your answer was quite comprehensive.

> On 1 Apr 2026, at 11:11 pm, Clem Cole <clemc at ccc.com> wrote:
> 
> Take a look at what I sent to whole list. If you have questions let me know off list. Clem
> 
> Sent from a handheld expect more typos than usual
> 
> 
> On Wed, Apr 1, 2026 at 6:11 AM Peter Yardley via TUHS <tuhs at tuhs.org> wrote:
> 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
> 


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