A Mainframe Tape Drive Emulator

Retro computer fans come in all shapes and sizes. Some like the big name machines from the dawn of the home computer era, others like collecting quirky pieces like early laptops and handheld devices. Even more obscure are those who choose to collect old mainframe hardware. This can be challenging, due to its relative obscurity and the limited resources available. [skaarj] is just one such fanatic, however, and has begun creating a PERTEC tape drive emulator for his Cold War era mainframe.

For those of us who didn’t work in industrial computing back in the 1980s, the PERTEC interface is an unfamiliar beast. It became somewhat of a defacto standard for connecting tape drives to mainframes. [skaarj] aims to understand and emulate this interface, creating a device with a full suite of capabilities. The PERTEC Whisperer is intended to be capable of reading and writing from PERTEC tape drives, including dumping tapes to an integrated SD card. The device will also be able to emulate a drive when connected to a mainframe.

Thus far, the adventure has already netted some successes. [skaarj] learned useful tricks, like rewinding a 9-track Qualstar 1260 with VHS tape, and how to pull apart the protocols involved using an old-school HP1662 logic analyzer. We can’t wait to see where the project goes next, and it might just have us hunting for a mainframe to call our very own.

19 thoughts on “A Mainframe Tape Drive Emulator

  1. The computer restoration scene is brimming with these impressive feats. Marc, Carl, and Ken Sherrif have showcased some similar wizardry. I look forward to the eventual stories about hacking together a way to read the antique SATA interface.

  2. In the 80s, Data point sold a tape drive emulator that connected their Data point 2200 desktop networked computers to a mainframe emulating both IBM tape drives and a IBM 1403 line printer.

    1. Do you have a link to some further information? I have a Datapoint 1551 Terminal without the disk drives, so I intended to make an emulator, but if Datapoint’s already done that, it will save me a lot of work

    1. Even talking about these on the wrong side of the Iron Curtain during the Cold War Era was dangerous. Nobody had any idea about those names or concepts or whatever Native Indian tribes have to do with early ATM banking computers, as nobody has any idea in the present. Remember this is a project from a place located on the other side of the planet where Vampires and Dragons are lurking in the shadows.

  3. Thanks for posting my project!
    So far I can dump tapes to sdcard (first successful attempt was on may 2nd) but it’s pain to replicate end-of-blocks and filemarks position. I need that to either write a new tape correctly or to transfer data properly to the mainframe.
    SIMH tape file format might do the trick.

    Oh and you forgot to mention: my beast is ransomware-free. No wannacry, petya, dharma, whatever. And no perversions such as hartbleed, intel management engine or speculative execution.

    You should also look at this post from an old hackaday article competition ran by Mike Szczys:


    This explains many things.
    Please feel free to take any part or the whole text and paste it into your article.

    1. “Oh and you forgot to mention: my beast is ransomware-free. No wannacry, petya, dharma, whatever. And no perversions such as hartbleed, intel management engine or speculative execution.”

      Now you did it, just by mentioning it, you’ve just woke up a bunch of haxorz who will want to be the f1rst to pwn you!
      Don’t pick up any SD cards you might find lying in your driveway!

      1. Old russian hax0rz to be precise, because most of the chips are labeled in cyrillic and made in the 80s.
        Most of those people passed away, the documentation is long-lost so hacking into this involves the dark art of necromancy or the traditional method of the soviets: kidnap ans torture.
        Younger hax0rs usually come to hack some cold beer.

    2. “Oh and you forgot to mention: my beast is ransomware-free. No wannacry, petya, dharma, whatever.”

      Not wanting to intentionally harm people is something to be explicitly mentioned now? Congratulations for having basic human decency then.

      “And no perversions such as hartbleed, ”

      You mean that your project is without the possibility of having a bug? Your hobby project, written by one person is sure to lack bugs, while a library that was written by nearly 400 people and is being used in thousands of programs had one that was undiscovered for two years? Great!

      1. Ladies and Gentlemem, when things get weird and i.possible to understand, follow the money and everything will come out in clear.

        I believe we uncovered somebody who is bothered by open-sourcing industrial pertec interface. So bothered that the anger interferes with the ability to process written information.

        Talking about money – such a converter to scsi or compact flash costs around US$5000 (search for the manufacturers, ask for quotation) and if it is also able to clone tapes then its value tripples.


        1. Talking about anger interference with written information: how is it possible for a single human being to write a perfect, bug-free full set of libraries for an entire huge old mainframe beast when it already has decades of tested software implemented with core-rope memory, programable memory and operating systems and was used by some army nuclear research institute?

        2. I said “my «beast»” – my big old mainframe
        – is immune to those vulnerabilities. Would you please prove the PDP11 family and newer beasts are vulnerable to the before-mentioned “perversions”? I am not asking about the 1980s soviet and romanian tech. They have a lot of bugs but getting them from remote to mine bitcoin or to encrypt files and ask for bitcoin – not going to happen.

        3. What is the connection between Intel Management Engine and Unibus/Multibus Interface?

        4. Talking about incomplete processing of written information but excluding anger – please read the following lines carefully:
        You uncovered a great secret which is helpful: please name that Pertec Interface library written by nearly 400 people and used in thousands of programs with two-years bug-free time interval. Please specify the url address where I can consult that set of pertec programs – because that little tiny obscure “hobby” project of mine – replacing the mainframe industrial tape drive with that small “hobby” sdcard thing – is not working yet. It is highly unstable, it’s real pain, I often get unexplained crashes or overflows, most of the software is written in assembly so no autocorrect stuff – and I did not start to implement the part which talks to the mainframe – yet;

        5. Who said I am the only one working on this, who said hobby and not full-time commisioned job with this project page serving as a periodic update for the people involved in this?

        6. Do you realize that every open-source software library started full of bugs from the work of one or a few people, and now serves modern, big “beasts”?

        7. Talking about decency – please share with us your studies, your degrees, your qualifications in hardware design and some of your projects. You can find mine if you read my other HaD project – the science-related logs. With your great ability to question everything maybe – instead of making fun of each other – we can start a big business, make tons of $ and both be happy.

  4. Bookmarked. The Pertec tape drive which has languished in my garage for around 30 years now should be revived.
    Just have to finish building an off-grid tree-change, move house, and set up the workshop. It would be a good time to see if the high speed paper tape punch still goes, too.

  5. I hope you have a power-truck to call your very own too. Those old mainframes can sure suck it down. And produce LOTS of heat in the process. LOTS of heat. Did I mention that they can produce LOTS and LOTS of heat?? You’ll be surprised at the amount of HEAT that can come off of one of those things…. ask me how I know ;-)

    1. CPU drawer released its magic smoke around 30 yearsA ago so it is bypassed through a microcontroller development platform. It is written somewhere in the text. So the heat is… acceptable.

      For the moderator: I accidentaly pressed (touched) a “report comment” button above and one comment vanished. Please fix that.

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