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Thread: M847 extended edition > Bootloader in PDP style !

  1. #1

    Default M847 extended edition > Bootloader in PDP style !

    I've been waiting for ages for my M993 PCB for my RK05.

    In the meanwhile I really started to hate all those toggle in programs over and over again.
    So I wanted a flexible bootloader. And since I was stuck on the RK05 (Waiting for that PCB)
    I've been playing with my PDP8/m and an Arduino...

    My design goals were:

    - make every M847 completely worthless
    - make a bootloader which contains all possible M847 boot loaders
    - put in all toggle in tests which I can think of
    - make a default loader possible by dip switches
    - make the original M847 still usable in the system
    - show selected program number in address lights
    - The project has to be in trough hole components
    - easy to find components
    - cheap!

    So I made use of these "friends".
    The very usable maintenance manual
    1 friend maintenance manual.jpg

    A wire wrap board which I used for a few small tests
    2 friend wirewrap board.jpg

    An Arduino Uno with an I/O expander and a LED status pcb
    3 friend arduino with custom pcb.jpg

    I've made the schematics and PCB in Kicad in the way I thought it should work.
    In the meanwhile I've developed the -almost- complete software using the
    DEC documentation on that little Arduino with a few add-ons...

    And guess what. The PCB for the RK05 and the bootloader arrived on the same day.
    I've ordered the bootloader PCB at jclpcb which produced and delivered them within a week! Bravo!

    4 bare boards.jpg

    Since the bootloader can be a great help for restoring the RK05 I
    choose to make the M847 extended edition PCB first.

    5 built M847 extended edition.jpg

    I had only one very tiny (and very nasty) bug in my software which I've developed
    in that week of waiting for my PCB. But than it worked just flawlessly right away...
    So I'm sorry it's not completely ready yet... So more postings to come....

    But here is a demo!


    And if that video doesn't work a direct link: https://youtu.be/0nqb3zyAv2g

    I've added the M847 extended version schematic on my website.
    I've added the component list as well

    I've called it the M847 extended edition, but in fact it is nothing like the real M847.
    You should look at this bootloader as an automatic front panel.

    The real M847 put's it's data at full speed into the memory.
    The PDP is actually running while a real M847 is copying it's diode data to core.

    The bootloader which I made puts the machine into single step mode, just like you do
    when you want to toggle in data into the front panel. But now it is a microcontroller doing it.

    Regards, Roland
    Last edited by Roland Huisman; October 25th, 2018 at 12:08 PM.
    WTB: RX8E / M8357 and Case for Altair 8800

  2. #2

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    Was that the serialdisk bootloader that you showed at the end of the video?
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  3. #3

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    Quote Originally Posted by m_thompson View Post
    Was that the serialdisk bootloader that you showed at the end of the video?
    Yes, the serial disk server runs on the laptop on the left.
    WTB: RX8E / M8357 and Case for Altair 8800

  4. #4
    Join Date
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    Default

    Bravo!

  5. #5

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    Quote Originally Posted by Roland Huisman View Post
    Yes, the serial disk server runs on the laptop on the left.
    I made a modification to the OS/8 BOOT command to boot from the serialdisk.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  6. #6

    Default

    Well done!

    My own method to minimise toggling is that I have a routine to load any of my bootstraps loaded right up at the 32k limit which reads the switches and boots the appropriate device. Not foolproof of course, but usually works ok.

  7. #7

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    Quote Originally Posted by m_thompson View Post
    I made a modification to the OS/8 BOOT command to boot from the serialdisk.
    Great work! The OS8 disk server, disk image manipulation
    and serial disk bootloader made many PDP's much more useful

    Quote Originally Posted by bobaboba View Post
    Well done! My own method to minimise toggling is that I have a routine to load any of my bootstraps loaded right up at the 32k limit which reads the switches and boots the appropriate device. Not foolproof of course, but usually works ok.
    Sounds like a good habit
    WTB: RX8E / M8357 and Case for Altair 8800

  8. #8

    Default

    Well done!

    I made custom boot-ROM's for my PDP-8A so it boots from serialdisk. First I started to build an adapter that should snap into both ROM sockets on KM8A. On the adapter should a bigger ROM sit and a switch so it would be possible to chose boot loader. But booting to serialdisk and then boot other devices from there was good enough.

  9. #9

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    Quote Originally Posted by anders_bzn View Post
    I made custom boot-ROM's for my PDP-8A so it boots from serialdisk. First I started to build an adapter that should snap into both ROM sockets on KM8A. On the adapter should a bigger ROM sit and a switch so it would be possible to chose boot loader. But booting to serialdisk and then boot other devices from there was good enough.
    Very nice, I've seen your repair story on that machine. Unfortunately I don't have a PDP8/a.
    I like the keyboard on the front. And I wonder if a bootloader like I built would work also in an PDP8/a.
    The /e /f and /m are all the same. As far as I know the original 8/m did not have toggle switches.
    But only a few of these are known. The most are having the same front panel as the /f.

    I think this board should also work in that original /m because that machine has the SW switch as well...
    WTB: RX8E / M8357 and Case for Altair 8800

  10. #10
    Join Date
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    Default

    I also must say, that is neat! My PDP8E uses serialdisk also which loads OS/8. I've been working on a hi speed paper tape unit and hope to have that done this winter. I was unaware of the M847 board. My machine didn't have that particular board, but maybe it is something I will be looking for in the future. Your 'bootloader' is something that would be a neat addition to most any PDP. Anyway, great job. Mike

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