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Thread: Model 12 BUS BOARD

  1. #1
    Join Date
    Feb 2014
    Location
    Netherlands
    Posts
    409

    Default Model 12 BUS BOARD

    I have a Model 12 without a busboard for more than a year now.
    I never succeeded in finding a card cage and bus board for this computer.
    At last I decided to build one myself.

    At first I found someone who sells the bus connectors as a start.
    There was no schematic available of the board, but with studying
    the Model II and Model 6000 schematics I found all I need for this job.

    Asking Pascal to draw the gerbers, he was in for help and is drawing them now.

    The project exists of a PCB with 3 bus slots and two flatcables with 40 wires each
    to connect to the motherboard. The termination of the lines is done.

    Here is a picture how it is going to look.

    BUS-M12.jpg
    The flatcables connects to K5 and K6 are to solder on the busconnector on the backside of the motherboard.
    In this mode K1, K2, K3 follow the connector on the motherboard, the video card stays on his place.

    There will be a second option, see this picture.
    option.jpg
    The leftside is the same as above, but the rightside has two connectors for the flatcables and a 80 bus edge connector,
    just like the one on the hans-02.

    You can mount the leftside anywhere you like and the connector on the rightside in the busconnector on the motherboard.
    The motherboard connector is now copied to C1. The videocard is inserted in C1 now.
    No need to solder on the motherboard.

    How far is the project.

    The gerbers for the leftside are nearly ready and can be tested.
    The rightside must be drawn (but is a stripped hans-02).

    If you are intrested in this project, please let me know.
    If you have any suggestions, please do.
    Last edited by Hans01; October 22nd, 2015 at 12:14 AM.

  2. #2

    Default

    @Han01 keeps on producing awesome hacks! Nice work!

    I too have pondered this idea as the Model 12 without a card cage is a neutered beast.

    One strong suggestion is to add more bus connectors. With only 3 slots available and with 1 taken by the video card, you can't have 68000 OS (e.g. Xenix) with a HD.

  3. #3
    Join Date
    Sep 2011
    Location
    Melbourne, Australia
    Posts
    970

    Default

    I like it. With the extra bus connector you can add a Model II HRG board and that is all I'd need because I don't use the 68000 functionality of my 8in TRS-80s

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  4. #4
    Join Date
    Feb 2014
    Location
    Netherlands
    Posts
    409

    Default

    @Ian and @pski

    I have limited the number of slots for two reasons.
    My first plan was to use it for the hans-02. The second was the costs of the PCB, which increase dramaticly above a certain size.
    I'll ask Pascal if it is possible to increase the number of slots.

    Ian, in that case you MUST move the video board to the bus. It is not tested but it seems possible to me.

  5. #5
    Join Date
    Sep 2011
    Location
    Melbourne, Australia
    Posts
    970

    Default

    So are there two 40pin busses on the M12 motherboard which the Hans-03 connects to? That gives a total of 4 slots (including the one on the M12 motherboard).

    You could theoretically add two long(ish) IDE cables and sit the Hans-03 outside of the case at the back or on top of the Model 12...

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  6. #6

    Default

    Quote Originally Posted by TRS-Ian View Post
    So are there two 40pin busses on the M12 motherboard which the Hans-03 connects to? That gives a total of 4 slots (including the one on the M12 motherboard).
    Ian.
    I think what Hans is proposing in option 1 is that you solder the (2) 40pin cables to the backside of the 80 pin slot on the main logic board. Option 2 is much more preferable as you don't need to modify (or remove) the main board. Hans please correct me if I am mistaken.

    You could theoretically add two long(ish) IDE cables and sit the Hans-03 outside of the case at the back or on top of the Model 12...
    There is so much empty space in the M12 that I'd have to find a way of keeping the cards in the case.

  7. #7
    Join Date
    Feb 2014
    Location
    Netherlands
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    Default

    @pski

    Option 1 gives you a total of 4 slots, but you need one for the videocard.
    Option 2 gives you a total of 3 slots (The slot on the motherboard is used to connect the exra bus)
    The videoboard moves to the first slot on the extra bus.

    There is so much room in a Model 12 to mount the extra bus, this seems no problem to me.

  8. #8
    Join Date
    Feb 2014
    Location
    Netherlands
    Posts
    409

    Default

    Just to show you the progress and give an idea about how it looks.
    Here some pictures of the Model II family bus extender.

    I hope to receive the last parts this week and then can test the board.

    HPIM0267.jpg HPIM0268.jpg HPIM0269.jpg

  9. #9

    Default

    I guess I could not sell you on adding more slots?

    I'm eagerly awaiting your testing results with different cards.

    BTW, something like this would be awesome for the Model I too, so that you can use more than one expansion device. I know I would be interested in that.

    e.g. http://www.trs-80.org/expandabus/

  10. #10
    Join Date
    Feb 2014
    Location
    Netherlands
    Posts
    409

    Default

    @all

    Some extra info about my Model II bus extender.
    In the poll about Model II owners there were 16 responders . Let we add another 16 for
    the guys who didn't respond, has more than one or has an other member of the Model II
    family.
    If I see the response on the PM's on my request for the hans-01, I must conclude that there is a very small
    group of users who want to improve their MII .
    That is one of the reasons why I had to set the number of slots to three. If you see how much the costs are
    sofar, you can see that higher costs would decrease the number of users. (sorry for you Pete)

    I would show you some extra options with the hans-04 (this new bus extender)
    If you build the the 2 boards and leave all the termination and pull-up resitors and connect the two boards
    with flatcables of about 40 cm. you can use the board to test or repair any other board in circuit.
    It is very easy to read signals or do mesurements.

    If you only use the busconnector part with two flatcables, you can monitor bus signals and levels in a very easy way.

    If you use the busconnector part you can easy connect devices to the bus.

    One serious warning.

    Pay attention to the orientation of the boards, check if all pin 1 positions are connected to each other.
    Pay attention to insert new boards in the right way in the new bus, take a look at the arrows.
    Connecting in the wrong way would surely damage the busconnector and most likely your computer !!


    You are warned !!!!

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