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Thread: Reading old tape backup

  1. #1
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    Default Reading old tape backup

    I have an old tape backup dating from around 1988. This was taken from a PDP-11 running (I'm fairly sure) RSTS/E, which we had at school and which was my first exposure to serious computing. I don't remember what kind of backup software was used to create it.

    I think it contains a multi-user adventure game that I wrote then. I've recently discovered that after I left school, someone took a partial backup of that, so I've had glimpses of some of the code and data. Rather sweetly, they wrote a perl version a few years ago which read the data files, as a nostalgic way of learning some new language features, which is still around.

    I've lugged it around from place to place. I don't know what the lifespan of these tapes is, but is there any possibility of finding something that could read this nowadays?

    tape.jpg

  2. #2
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    Quote Originally Posted by edwh View Post
    I have an old tape backup dating from around 1988. This was taken from a PDP-11 running (I'm fairly sure) RSTS/E, which we had at school and which was my first exposure to serious computing. I don't remember what kind of backup software was used to create it.

    I think it contains a multi-user adventure game that I wrote then. I've recently discovered that after I left school, someone took a partial backup of that, so I've had glimpses of some of the code and data. Rather sweetly, they wrote a perl version a few years ago which read the data files, as a nostalgic way of learning some new language features, which is still around.

    I've lugged it around from place to place. I don't know what the lifespan of these tapes is, but is there any possibility of finding something that could read this nowadays?

    tape.jpg
    Sure. At Update we have an 11/70 running RSX, which have a TU81. That means we can read 1600 bpi and 6250 bpi tapes easily. However, that is in Sweden.
    But I'm sure there are others around the world as well.

    If someone comes with an 800 bpi tape, we could probably deal with it as well, but it would require some work. We have two TU77 in storage, with status unknown these days. But with some work, we should be able to get atleast one running.

    With a little patience, you can see the machine, including the tape drive here: http://magica.update.uu.se/. And the web page is served by that same machine...

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    You need to be carefull with such a tape if you want to recover the data. "Baking" can help. This is about Audio tape but computer tape can suffer in a similar way.

    https://en.wikipedia.org/wiki/Sticky-shed_syndrome

    It might also suffer from print through where the magnetic pattern from one layer affects the next.

    As you haven't put a state in your profile its hard to recommend places, but some one experienced would be good. If you are west coast USA then the Computer History Museum might help, on the east coast Dave McGuire who has a small museum in Pittsburgh with a working PDP11 and 9-track drives, VCF in Wall, New Jersey who host this forum in Wall, or the Rhode Island Computer Museum.
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

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    Ah, sorry, I should absolute have said where I am. I'm in the UK, more specifically fairly close to Preston.

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    If it's a 9 track tape from a PDP-11, it's not old in the sense of open-reel tapes. I've handled tapes from the early 1960s successfully. Of course, they were 7 track, but you get the idea.

    Now, if this was a 10 year old SSD, I'd say "forget it".

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    Sorry, I should of course have said where I am. I'm in the UK, specifically near Preston.

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    Quote Originally Posted by edwh View Post
    Sorry, I should of course have said where I am. I'm in the UK, specifically near Preston.
    If you add your location to your profile it will show in your posts.

    If you ask on the "Dec Legacy" group :-

    https://groups.io/g/declegacy

    there should be some one who can help. There is some one close to you who I think has round drives.

    https://wickensonline.co.uk/declegacy/

    if that fails TNMOC should be able to help. I don't think they have RSTS but they have a 11 with round tape drives.
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

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    Thanks Dave, I'll drop that guy a mail.

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    One additional thing: Depending on the age of the PDP-11 system, the tape may be recorded as 800 BPI, NRZI. Most 9 track drives do not have the capability to read this density, as its popularity was quickly eclipsed by 1600 PE and 6250 GCR densities that packed more on a tape and were more reliable. A few months ago, I handled one such tape from a PDP-11; indeed, the 800 density was even used on early VAX systems.

    So be sure that whoever does your tape has the capability. Oh, and the manufacturer's label that says "6250 certified" or some such has absolutely nothing to do with the density of the data on the tape. I've had such tapes recorded at 200 BPI 7-track (even parity yet!) come through my shop.

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    Quote Originally Posted by Chuck(G) View Post
    One additional thing: Depending on the age of the PDP-11 system, the tape may be recorded as 800 BPI, NRZI. Most 9 track drives do not have the capability to read this density, as its popularity was quickly eclipsed by 1600 PE and 6250 GCR densities that packed more on a tape and were more reliable. A few months ago, I handled one such tape from a PDP-11; indeed, the 800 density was even used on early VAX systems.

    So be sure that whoever does your tape has the capability. Oh, and the manufacturer's label that says "6250 certified" or some such has absolutely nothing to do with the density of the data on the tape. I've had such tapes recorded at 200 BPI 7-track (even parity yet!) come through my shop.
    All correct, with the small caveat that with regards to PDP-11 systems, it is 6250 which is very unusual. The only supported tape drive that could do it was the TU81.
    From the top of my head:
    TS03 - 800 bpi
    TSV05 - 1600 bpi
    TS11 - 1600 bpi
    TU10 - 800 bpi
    TU16 - 800/1600 bpi
    TU45 - 800/1600 bpi
    TU77 - 800/1600 bpi
    TU80 - 1600 bpi
    TU81 - 1600/6250 bpi

    So - 800 bpi was actually very common to find for these machines. It might be trickier today with modern tape drives, but anyone keeping these kind of systems around, and which have a working tape drive, there is a fairly big chance he can deal with 800 bpi as well.

    (And for people who like details, I have not mentioned the TE drives, as they as just the same as their TU counterparts. I have also not mentioned the TU78, which was not officially supported on the PDP-11, nor any TA drives, which all have STI interface, which pretty much means only connected through HSC.)

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