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Thread: Questions about a secondary 8-bit ISA floppy controller in an Amstrad 1640DD

  1. #1

    Default Questions about a secondary 8-bit ISA floppy controller in an Amstrad 1640DD

    Hi,

    My first post here in this forum. No longer a mere lurker.
    So, I bought this 8-bit ISA floppy disk drive + serial port controller: http://www.malinov.com/Home/sergeys-...a-fdc-and-uart to use in an Amstrad 1640DD PC.
    The computer comes with two 5.25" 360KB floppy disk drives and my goal was to connect a 2.88MB disk drive to the new FDC controller and have it replace the second 5.25" drive.

    The problem is that I just can get the computer to finish the POST if the board is installed. Even if I disable the ROM or disconnect the floppy disk drive. Just by having the board installed in any expansion slot, the computer won't complete the POST.
    The error is something like "Error: Failure of Floppy Disk Controller or Drive". I notice that it happens as soon as the floppy drives are scanned during POST, even before the BIOS tries to boot the OS.
    It's the same error that I get if both 5.25" floppy drives are disconnected or if I disconnect the A: drive -- disconnecting the B: drive is OK.

    I think that the FDC controller is conflicting with the onboard FDC controller, which cannot be disabled. But this happens whatever BIOS address I pick for the board and even when I disable the ROM. So I think that it could be an isse with the I/O address range. If this is the case, there's nothing in the documentation for the board on how to change that.

    Can somebody help me fix this? Or is it confirmed that the board won't work in an Amstrad 1640PC?
    I already have an XT-CF-Lite 4.1 with a 2GB CompactFlash card (and DOS 5.0) that's working just fine...

    BTW, this is drive that I'm trying to connect: https://www.ebay.com/itm/2-88MB-Flop...72.m2749.l2649
    It takes power from pin 3 of the 34 pin flat cable, which is supported by the FDC controller and the LED lights up during POST at the same time as the internal A: drive. But the POST fails even if no drive is connected...

  2. #2

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    Do you have a driver that supports a secondary floppy controller? I don't think you can get it to work - and the card doesn't support changing the I/O address.

  3. #3
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    Surely there's a way to disable the primary--even if it means cutting a trace.

  4. #4

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    Quote Originally Posted by mcs_5 View Post
    Do you have a driver that supports a secondary floppy controller? I don't think you can get it to work - and the card doesn't support changing the I/O address.
    Thanks for replying. Not sure what you mean when you ask if I have a driver that supports a secondary floppy controller... Regarding the I/O address, if it can't be changed, which is most likely the case, then I have no use for the board, as the onboard FDC cannot be disabled easily (or at all).

  5. #5

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    Please have a look at this: https://github.com/skiselev/floppy_bios.
    It enable you to have up to 8 floppies. OK, that is not what you need but it should be good enough to act as a driver for your second FDC. But it only works when using a card with a different I/O address.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  6. #6

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    Quote Originally Posted by Ruud View Post
    Please have a look at this: https://github.com/skiselev/floppy_bios.
    It enable you to have up to 8 floppies. OK, that is not what you need but it should be good enough to act as a driver for your second FDC. But it only works when using a card with a different I/O address.
    Secondary FDC Configuration
    ---------------------------

    Currently the BIOS extension does not support DMA channel and IRQ sharing with
    the primary FDC. Therefore the secondary FDC must not use DMA channel 2 and
    IRQ 6.
    That makes it a bit useless

  7. #7

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    Quote Originally Posted by maxtherabbit View Post
    That makes it a bit useless
    Yeah, I never quite understood why Sergey didn't implement jumpers or something to change the DMA/IRQ of his FDC. I think they'd get a lot more use that way.

    (I'd also like to put it out there that the original Shugart interface allowed for up to 16 different drives on one cable, using the 4 Drive Select jumpers as a binary address. Unfortunately, I don't think many microcomputer-era drives actually support that, and even fewer controllers.)
    Current favorites: IBM 5160 (EGA+Hercules+PGC, 4 floppies, XT-IDE), DCC D-116 (Nova 1200 clone), ASR 33 Teletype (now FULLY armed and operational! Mostly.)
    Wishlist: IBM 5161 (expansion chassis), IBM 5175 (monitor for PGC), Data General Nova IO / peripheral cards, and the meaning of life.

  8. #8

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    Quote Originally Posted by Nevets01;609190(I'd also like to put it out there that the original Shugart interface allowed for up to [I
    16[/I] different drives on one cable, using the 4 Drive Select jumpers as a binary address. Unfortunately, I don't think many microcomputer-era drives actually support that, and even fewer controllers.)
    I am sooooo used to deal with PC FDCs that I completely forgot about this. What about adding a 74138 or 74154 (+ bus drivers) to handle 8 or 16 drives? Then add an extra board that does provide the needed headers so one can still use the normal cables and drives. No second FDC card needed and we can uses Sergey's software (after altering it a bit) for driving all those drives.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  9. #9
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    Quote Originally Posted by maxtherabbit View Post
    That makes it a bit useless
    I don't understand why the thing doesn't support IRQ and DMA sharing with the primary controller. That's what bit 3 is for in port 0x3f2.

    Seems to me that I passed some driver code along to one of the forum members that supported a secondary controller in this manner not that long ago.

  10. #10

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    Quote Originally Posted by Chuck(G) View Post
    I don't understand why the thing doesn't support IRQ and DMA sharing with the primary controller. That's what bit 3 is for in port 0x3f2.

    Seems to me that I passed some driver code along to one of the forum members that supported a secondary controller in this manner not that long ago.
    Indeed, I'm still working on a build for release but it's coming along

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