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Thread: FreHD on Tandy 6000?

  1. #1
    Join Date
    Jul 2005
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    Default FreHD on Tandy 6000?

    Has anyone done any work on interfacing FreHD to a Tandy 6000? My two original 15MB drives are still working, but who knows how long that will last?

  2. #2
    Join Date
    Jan 2014
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    Western North Carolina, USA
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    Some work has been done by Fred and Ian; there were still issues as I recall. One root issue, as I recall, was that FreHD uses some of the Z80CTC ports for other functions, but the Z80CTC on the hard disk interface card is required for Xenix HD operation (the CTC generates the Mode 2 interrupt vector necessary). Fred or Ian can talk with greater knowledge than I, but that's one thing I recall. LS-DOS 6.3.1 does not require the CTC, as the LS-DOS 6 HD driver doesn't use interrupts.

    I'm not sure that the xtrs code on which FreHD was based emulates the IRQ capability of the WD1010 chipset, and even if it does I don't know how well-tested it is.
    --
    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

  3. #3

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    Quote Originally Posted by lowen View Post
    Some work has been done by Fred and Ian; there were still issues as I recall. One root issue, as I recall, was that FreHD uses some of the Z80CTC ports for other functions, but the Z80CTC on the hard disk interface card is required for Xenix HD operation (the CTC generates the Mode 2 interrupt vector necessary). Fred or Ian can talk with greater knowledge than I, but that's one thing I recall. LS-DOS 6.3.1 does not require the CTC, as the LS-DOS 6 HD driver doesn't use interrupts.

    I'm not sure that the xtrs code on which FreHD was based emulates the IRQ capability of the WD1010 chipset, and even if it does I don't know how well-tested it is.
    The main issue is that I don't have access to a model 2/12/16... so I can't test. I tried to enhance the pic firmware to handle the interrupt, but again without a machine, it's almost impossible to debug. I am since looking for a model 2/12/16, but so far, none has become available near me (Luxembourg or Belgium)...

    -Fred

  4. #4
    Join Date
    Jan 2014
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    Quote Originally Posted by veco View Post
    The main issue is that I don't have access to a model 2/12/16... so I can't test. I tried to enhance the pic firmware to handle the interrupt, but again without a machine, it's almost impossible to debug. I am since looking for a model 2/12/16, but so far, none has become available near me (Luxembourg or Belgium)...

    -Fred
    The acid test would be Xenix 3.2, but you need the upgraded 68K boards (6MHz with a PAL swap or the 8MHz).

    We could probably write a driver for LS-DOS 6.3.1 that required the IRQ, but trying to debug a driver and FreHD at the same time would be difficult. The Model II/12 TRSDOS II 4.2 can be hard disk ready; I've never run TRSDOS II from a hard disk, though, so I have no idea how that works. Xenix isn't very difficult from the user interface to set up, but there is no source in the wild and z80ctl (which does all the I/O) is famously obfuscated. It might be possible to reverse-engineer z80ctl and drop a non-IRQ HD driver into it, but it might be easier to get IRQ's working in FreHD.

    And this all assumes the Tandy interface board; the Hans-01 board has no CTC and thus won't work. It would be nice if FreHD could do the Z80CTC emulation, but there may not be enough code space in the PIC to hold it.
    --
    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

  5. #5

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    Quote Originally Posted by lowen View Post
    The acid test would be Xenix 3.2, but you need the upgraded 68K boards (6MHz with a PAL swap or the 8MHz).

    We could probably write a driver for LS-DOS 6.3.1 that required the IRQ, but trying to debug a driver and FreHD at the same time would be difficult. The Model II/12 TRSDOS II 4.2 can be hard disk ready; I've never run TRSDOS II from a hard disk, though, so I have no idea how that works. Xenix isn't very difficult from the user interface to set up, but there is no source in the wild and z80ctl (which does all the I/O) is famously obfuscated. It might be possible to reverse-engineer z80ctl and drop a non-IRQ HD driver into it, but it might be easier to get IRQ's working in FreHD.

    And this all assumes the Tandy interface board; the Hans-01 board has no CTC and thus won't work. It would be nice if FreHD could do the Z80CTC emulation, but there may not be enough code space in the PIC to hold it.
    One can always make a FreHD v2, using a more powerful microcontroller. Any ARM-code or PIC32 comes to mind, they are cheap and easy to work with... Or even an FPGA based solution. But dealing with the IRQ in the FreHD is doable, the GAL has one or two spare signals, and so does the PIC18.

    -Fred

  6. #6

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    I've got a spare 16b. Anyone want to come get it and take care of shipping it to Veco? Reply via PM or to my email.
    Kelly

  7. #7

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    I want a Model II FreHD as much as anyone and I will be willing to help out with getting it working.

    However, there are a few options available now for Model II solid state hard drives:

    David Gesswein's MFM Emulator
    http://www.pdp8online.com/mfm/

    The Drem MFM Emulator
    http://www.ebay.ca/itm/-/301968006996

    There are some other propriety solutions if you search for Solid State MFM.

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