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Thread: M847 extended edition > Bootloader in PDP style !

  1. #71

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    In the last weeks I've worked quite intensively with my PDP8/M to update SpaceWar.
    And there were a few things which annoyed me on the current BIN loader...

    1- You always needed to set 7777 into the switch register. Very annoying when you
    upload a new version of your program and set the switches to 7777 and then back
    again to the start address of your program.

    So I've edited the BIN loader. When I start it now it always uses the serial port.
    No need to set the 7777 every time. The downsize might be that you can't use the
    much slower 'high speed' papertape reader with this BIN loader..

    2- Normally I have a slow dumb terminal on my primary 03/04 serial controller. But I want to
    upload my software which I made on my PC pretty fast. And also loading other
    paper tape images going slow. For this purpose I swapped even boards.

    But many people have a secondary serial port set at a higher speed for the OS/8 disk server.
    So I've made a second version of the BIN loader which is able to load paper tape
    images trough the secondary serial port into core. That goes pretty fast. And when you
    start your loaded program, it shows up at the normal primary console like always.

    Before I release this stuff I've been thinking to change the boot order a bit as well.
    When I started the project I just put in everything I could find. But I think
    it would be nice to make it more logic like this for example:

    01 OS8 disk server load 40/41
    02 RX01 (RX8 )
    03 RX02 (RX28 )
    04 RK05 (RK8E)
    05 TU56 (TD8E)
    06 TU56 (TC08 )
    07 TU60 (TA8E)

    10 PC04 (PC8E)
    11 RIM loader 03/04
    12 BIN loader 03/04
    13 BIN loader 40/41
    14 Kaleisoscope
    15 MI8-EE Typeset
    16 MI8-EF Edu sys low
    17 MI8-EG Edu sys high

    Suggestions are welcome. Also about the BIN loader.
    Is it useful for others to implement it this way?
    Or am I the only one here complaining about that 7777 ?

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  2. #72
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    Yeah that is a change I made to the DEC standard BIN loader I use all the time. Here: https://www.ak6dn.com/PDP-8/MAINDEC/Binary_Loaders/ as dnnbin.*
    Uses low speed console only, no SW test in the loader at all. Much more convenient.

  3. #73
    Join Date
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    Location
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    Quote Originally Posted by Roland Huisman View Post
    Is it useful for others to implement it this way?
    Or am I the only one here complaining about that 7777 ?
    I forget to set the switch all the time and then wonder why the program won't load.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  4. #74

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    I really like the memory/bootloader card. Once I got used to it, my testing was much faster! What I would like to have, is to save some own code in it. I would like it if this would be easy to do, because I'm not used to Arduino/Atmel and so on.
    My last project uses a terminal at 03/04 and a serial puncher at 30/31. So I modified the RIM loader and BIN loader.
    My trick was to load the modified loader from OS/8 (with os8diskserver) with ABSLDR and then HALT the machine. Once the Loader is in RAM, it is only destroyed by starting OS/8 again. So the change from OS/8 to the modified Loader and back is quite easy.
    But I really would like to put such code direct into the card.

    have fun
    Volker

  5. #75

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    Quote Originally Posted by AK6DN View Post
    Yeah that is a change I made to the DEC standard BIN loader I use all the time. Much more convenient.
    Thanks! Glad that I'm not the only one

    Quote Originally Posted by m_thompson View Post
    I forget to set the switch all the time and then wonder why the program won't load.
    So did I So I will put this update into the new version.

    Quote Originally Posted by gnupublic View Post
    What I would like to have, is to save some own code in it. I would like it if this would be easy to do, because I'm not used to Arduino/Atmel and so on.
    Hi Volker,

    The project is completely open source. You can put your own bootloaders in it.
    At the top of the code is explained how your code should look like. It is very simple. See one of the .ino files.
    https://github.com/Roland-Huisman/M8...d-version-V1.1

    There are many how-to video's on how to upload new firmware into an Arduino.
    If you want I can guide you trough the process...

    But when I look at the board from Vince it seems that he did not place the MAX232A.

    So the first thing to do is to place a MAX232A onto the board together with the
    90 degree 40 pin connector. Then you can upload your own code to the bootloader.
    All you need is a BC01V cable (use one of your serial cards) and a cross cable to a comport of your PC.

    Another option: When you have an Arduino UNO board you can change the chip and
    program it using the Arduino. After that you place the chip back on the bootloader.

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  6. #76

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    Thanks for the hints. The file format is simple to understand. I'm not familar with Arduino, but I will give it a try to embed KillTheBit.... Arduino Duo is on order.

    I saw that you can put in code up to "Program_77[]". Despite the default Switch, is there any possibility not to toggle 63 times?

  7. #77

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    Quote Originally Posted by gnupublic View Post
    Despite the default Switch, is there any possibility not to toggle 63 times?
    Ah! Thanks for reminding me on that! I wanted to make an auto increment on it.
    This saves the front switch. I'll add it to my to-do list.

    Thanks!
    WTB: Case for Altair 8800 ...... Rolands Github projects

  8. #78

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    ...don't forget to make the start blinking lights customisable....
    Is it possible to read out the SR for choosing the program number?

  9. #79

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    Quote Originally Posted by gnupublic View Post
    ...don't forget to make the start blinking lights customisable....
    You can edit the code and make something else. That is the beauty of open source.

    Quote Originally Posted by gnupublic View Post
    Is it possible to read out the SR for choosing the program number?
    No... Unfortunately the switches can't be read directly... You need more hardware on the bootloader to actually
    let the CPU read out the switches into AC. And after that you have to read out de AC contents with the bootloader.

    Besides that, you have to write the command into memory somewhere before you can actually
    give the command to the PDP to read out the switches. I don't want to write into memory because
    maybe someone has something important stored at this location.

    And when you are debugging a machine with a hardware fault it can also be a problem.
    You might not be able to select any program due to a defect in your machine. The SW switch
    is tied directly onto the bus an can always be read.

    These were my design considerations to make it this way. And besides all that it is cheaper to built it this way.

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  10. #80

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    I've released V1.7 with modified boot order and modified BIN loader like mentioned earlier.
    Also added the secondary modified BIN loader. And there is a new file with bootstrap numbering.

    https://github.com/Roland-Huisman/M8...d-version-V1.1

    When I have a bit more time I will add the auto increment to the bootloader.

    Regards, Roland
    Last edited by Roland Huisman; November 13th, 2019 at 12:58 PM.
    WTB: Case for Altair 8800 ...... Rolands Github projects

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