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Thread: 8-Bit IDE Controller

  1. #21
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    I suspect 2 layer should be enough. This is about as simple as it gets.

    My coworker just gave me a couple ads for PCB mfg and they go something like this:

    2 layer PCB, up to 60" sq, free silkscreen, tooling and mask, for $25.
    No minimum qty.

    So, at 60 square inches, I'd think we could drop 4 or more of them onto the same board.
    If we were able to assemble them ourselves, the cost could easily be $20 or less per board. (I've no idea what the parts would cost)

    That ASCII schematic as seen here:

    http://www.mylinuxisp.com/~jdbaker/o...cecode/xtide.c

    didn't have an option ROM on it, so I think we'd be better off trying to clone one of these ADP50L boards. So that would require a hi-res scan of both sides of the PCB, a dump of the option ROM, and perhaps a few hours with a multimeter to make sure all the connections are known.
    If anyone else can handle the PCB layout, schematics and hardware end of it, I am all over the option rom side of it...

  2. #22
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    I did the initial chip and connector placements last night and PCB123 is predicting the PCB will cost about 10 bucks US each in a quantity of 25.

    That's a 2.5" x 3.5" XT board with room for a ROM and a dip-switch (which was mentioned but not shown in the schematic) either of which will, no doubt, signifigantly change the layout.
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  3. #23

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    The project sounds amazing, with the add of the bios boot rom, and if you can brake the 512mb barrier, that card will be the dream of all xts fans.

    With a simple ide to cf adapter you can use cfs with 0 noise, no mecanic parts and preserve the longevity of the xt machines.

    Many old machines have this solution, spectrum divide, msx sunrise, etc, I think is the pc turn to have a modern standard storage card adapter.

    Go ahead with the project, and good luck !!!

    Offtopic:

    If its possible to adapt usb protocol to isa bus, for obtain an usb host adapter, for keyboards, joysticks, hd drives, etc ???
    I think usb protocol is designed for pci bus, but perhaps can be adapted to isa one........
    Imagine an xt with usb devices................DREAM IS FOR FREE!!!

  4. #24

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    Quote Originally Posted by genocho View Post
    Offtopic:

    If its possible to adapt usb protocol to isa bus, for obtain an usb host adapter, for keyboards, joysticks, hd drives, etc ???
    I think usb protocol is designed for pci bus, but perhaps can be adapted to isa one........
    Imagine an xt with usb devices................DREAM IS FOR FREE!!!
    It is theoretical possible (if not the transfer-speed exceeds the system bus). All you need is an adaptor (with volt reducers and some controllers), and a Homemade DOS driver. And of course, a Homemade DOS USB Driver for the actual device you have connected to the card.

    It would of course take years (escapely because every single USB device need it's own device-driver), but I agree, it would have been cool.

  5. #25

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    I have a Tandy 1000TL/2 that the HDD controller on the MB failed. I am using a 8 bit XT ide card to run a CF card. I have 2 XT ide cards and only one would work with the CF card in the TL/2. The one card I have is a Seagate ST-05x card. this one did not reconize the CF. The other is a Silicon Valley card ADP50 ??(forgot which one till I boot up the TL/2)which works really good on the TL/2.
    Some of the boot BIOS may not reconize the CF cards or it was the TL/2 being picky, not sure till I get another CF adapter and get the IBM 5150 running with the Seagate card.

  6. #26
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    Quote Originally Posted by Druid6900 View Post
    I did the initial chip and connector placements last night and PCB123 is predicting the PCB will cost about 10 bucks US each in a quantity of 25.

    That's a 2.5" x 3.5" XT board with room for a ROM and a dip-switch (which was mentioned but not shown in the schematic) either of which will, no doubt, signifigantly change the layout.
    Fantastic! I was given some winBoard PCB layout software by my coworker this morning, but it appears you've got it all under control. (thank you for taking it!)

    We absolutely need an option ROM on the thing, as well as the bank of dip switches or jumpers to move the address decode around as one would expect on such a card. I suspect a 16k rom at most would be required, having it flashable or at least eeprom programmable is ideal (and socketed), since I don't have a UV eraser at my disposal, but I do have a burner. The BIOS, while most of it stolen from other option ROMs from similar boards, will all be open source.

    Questions:
    Do we want the I/O decode to be selectable from 1f0 to 170, so you could theoretically put 2 of these boards into a machine?
    I don't see any reason why it shouldn't be able to support 2 drives at a minimum.
    Do we need CDROM support? I'm not sure what implications this will have on the option rom code. It won't be a priority for me to code, that's for sure.
    Can you even run MSCDEX on an 8088?

    wow. just wow.

  7. #27

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    I'm glad to see this thread takeoff like this ... I've looked at the IDE interface quite a bit recently while helping some poor guys hack their Gridcase machines to take other hard drives.

    • Definitely design the I/O decode to handle alternate ports. You will probably need to debug this on a machine with an existing hard drive.
    • MSCDEX will run on an 8088. I run it on a NEC V20 equiped PCjr when I use a SCSI setup.
    • The hard part is the ROM.


    So just to be sure I understand, you are going to design the interface to work with 16 bit drives? This is going to require latching all 16 bits from the drive, then feeding it back to the machine 8 bits at a time over two distinct I/O cycles. All of the control and status registers are 8 bits so it is not a problem, but the 16 bit I/O for data will require latching.

    That's going to require the option ROM to do an I/O cycle for the first 8 bits, then change addressing on the board to be able to access the second bits before the next I/O cycle.

    The good news about the ROM programming is that the bare minimum can be found in the AT technical reference, which was designed with MFM controllers in mind. (IDE is a superset of MFM.) You can learn a lot looking at the BIOS listing and do the debug work of latching and moving the extra bits with an existing known good base to start from.

  8. #28
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    Or you could just fageddabout the upper 8 bits; IDE storage is cheap & plentiful.

    m

  9. #29

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    I'm not worried about cutting the capacity of the drive in half. I'm more worried about sector addressing issues.

    If you do it that way, then you wind up with the equivalent of 256 byte sectors when they should be 512. Compensating for that is worse than just doing it correctly.

    That trick is acceptable on an 8 bit micro where there is no existing API or expectations about sector size. It's not so hot for a PC solution.

  10. #30
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    Quote Originally Posted by MikeS View Post
    Or you could just fageddabout the upper 8 bits; IDE storage is cheap & plentiful.

    m
    So, a 1Mb drive would actually store only 512K? I could live with that.

    --T
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