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Thread: KAYPRO and KayFreHD as a hard disk module

  1. #1

    Default KAYPRO and KayFreHD as a hard disk module

    Hello Kaypro Users,
    the first prototype for the KayFreHD module had arrived today and works fine at once.
    This extended Version of the FreHD module has extra logic and connector for the use in Kaypros.
    It get power over the standard Kaypro flat cable. So is no need for an extra power connection.
    The first two pictures shows the use in an Kaypro 4/84. The KayFreHD module is direct connected to the J9 header on the mainboard.
    The fourth picture shows the use of the KayFreHD in an Kaypro 4/83. There is no I/O connector like in the newer Kaypros.
    The "J9" is then on the piggy back board, which is plugged in the Z80 socket. On the board there are bus drivers, some inverters and TTL-logic.
    The second 50pin header on the KayFreHD is for the use in the TRS-80. Then you have to remove one LS04 and change the jumper setting.
    If there some people who wants this board/board set, i produce a little batch of these boards. Please let me know.
    Many thanks to JAQ, without his knowledge, this project wasn't ready until now.
    DSC_0201.jpg DSC_0202.jpg DSC_0205.jpg DSC_0204.jpg

  2. #2


    Well done! Very cool!.

    My vintage collection:
    My vintage activities blog:
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)

  3. #3


    Thanks Tez.
    Here is an picture from the PCB, to see the detail for jumpers.

  4. #4


    All tests succesfully done with the prototype PCB.
    Also in the TRS-80 it works perfect.
    The second picture shows the complete populated board.
    PS.: Questions are welcome.
    image0002.jpg image0001.jpg

  5. #5


    Can the original FreHD be used for this? That's what I've got right now.


    Proud owner of 80-0007 - The only one of its kind.

  6. #6


    Frank, I've got an original FreHD card that I haven't got around to assembling. I guess my question is similar to geneb. Can I use this for the Kaypro? ...or do I need to get a card off you? I assume I'll have all the components I need if I've already got the FreHD kit, yes? How much are your cards?

    My vintage collection:
    My vintage activities blog:
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)

  7. #7


    Yes, the original FreHD PCB is usable.
    First you have to build a adapter board, which changes some pins from the Kaypro I/O connector to the FreHD module.
    Five TTL inverters (LS00 or LS04) are required on the adapter board. Then a special firmware is needed for the use with the Kaypro's.
    The special firmware works also with the TRS-80. A schematic and a useful layout for this adapter is attached below.
    This board is enough along with the FreHD module for using with the newer Kaypro's (1/84, 2/84, 2X/84, 4/84, 4X/84, 10/84, 12X/84, Robie).
    For older Kaypro's (2/83, 4/83) you have to have the Z80 piggy back adapter board too along with the EPROM modification for 2764 types.
    KAYPRO_FreHD Adapter.pdf KAYPRO_FreHD Adapter_2.jpg

  8. #8
    Join Date
    May 2012
    Auckland, New Zealand


    If you are using /84 machines then Frank's adaptor design is a great way to use the TRS-80 FreHD.

    If you are using a 4/83 (and hopefully the 2/83 - Tez - Phil Avery is going to lend me his for testing) the approach that requires least modification to the machine is a piggy back adaptor board with both a ROM and Z80.

    This is required because the ROM on the /83's is too small and doesn't have sufficient decoding on the main board to support the KayPlus firmware. Also because there is no expansion connector like the /84's.

    This is the approach I took when Frank and I were working on the project (because I have a 4/83). I built a single adaptor board that plugged into the ROM and Z80 sockets. It does require two additional wires to be soldered to one other chip on the main board but is easily reversable if you want to return the machine to "stock" configuration. The connector on this adaptor allows a "TRS-80" FreHD to be used with a straight through 50 pin cable.

    Some photos of the prototype board are shown below. I have done a layout for it and am waiting for some PCB's to arrive. They don't get delivered to me as quickly as to Frank.

    BLOG_KP1.jpg BLOG_KP2.jpg

    And you do need updated PIC firmware on the FreHD. This is still compatible with the TRS-80 but adds support for 512 and 1024 byte sectors and improved WD1002 controller compatibility.

    From a functionality standpoint there is no difference between this and Frank's designs. Both will run the KayPlus firmware (Advent only on the /84's but hopefully one day we will find it for the /83's) and boot directly from the FreHD.

    I hope to get a write up on the project completed and onto my blog in the next week.
    Last edited by jaquinn; January 6th, 2014 at 09:59 AM.
    SBC6120 / PDP11 + VAX / TRS-80 / Kaypro / Northstar / Home Brew Z80 / BBC / Amstrad / Commodore

  9. #9


    Is there a place to purchase the FreHD-Kaypro adapter board?


    Proud owner of 80-0007 - The only one of its kind.

  10. #10


    Hello Geneb,
    depending on the interest, the board are available soon. Details follow.


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