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Thread: Identifying Shugart interface 5.,25" floppy drives

  1. #1

    Default Identifying Shugart interface 5.,25" floppy drives

    Hi folks,

    I've got myself royally confused with the differences between Shugart and IBM interface floppy drives and I'm puzzled as to why some drives I have that 'should' be Shugart (based on age of the machine it was removed from eg STM Pied Piper CP/M box) will work in the floppy imaging PC I built recently which uses a Winbond SuperIO floppy controller.

    This all came about because I've been working on a PPG Waveterm A synthesizer which originally used 8" Shugart drives but was modified to use a YE-Data YD380 HD drive with a 50 pin to 34 pin cable adapter.

    Is there a way of visually identifying which signalling method is used, eg tracing lines from the card edge connector or maybe the number of drive select pins? I know Shugart has 4 drive select lines while IBM only has two. Some of the drives I have seem to be difficult to find documentation on and obviously to troubleshoot them I need to connect them up to the right type of host.

    Cheers!
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  2. #2
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    The interface for shugart and PC is the same at the DRIVE end. It differs only at the controller end.

    Most early 5.25" in IBM PCs have all four drive select jumpers. In an IBM PC they are always set to the second drive.

    Later drives, especially 3.5" drives omit the "unused" drive selects. Those can still be used on a "Shugart" style controller, but only as the second floppy drive. (Or first and second if it has at least a DS A/B or 0/1 switch, but not third or fourth).

    Controller pinouts for both Shugart and PC are shown here:
    http://old.pinouts.ru/HD/InternalDisk_pinout.shtml

    I don't know any good way to tell the difference electrically. But if drives are already present, a "Shugart" style system will have a flat cable, and an IBM PC style system will have a twisted cable. A controller mismatch will cause drives not to become active and/or their motors to not run or do so at the wrong time.

  3. #3
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    What needs to be checked would be jumpers to make sure those match the non-IBM requirements. Some of the later 80s drives do not have jumpers but have solder pads that be used for that. Very inconvenient if planning on swapping drives between PC and non-PC systems because soldering and then unsoldering is necessary. If the drive has neither jumpers nor solder pads, it will most likely only work with an IBM PC style controller.

    The only knowledge I have of the Waveterm comes from http://www.hermannseib.com/english/s...g/wtfloppy.htm I think that most 5.25" high density floppy drives would work if the motor jumper and ready jumper are changed from the settings for AT use. I don't have the device to test though.

  4. #4

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    Hi folks,

    Thanks for the links, I've been all over Hermann's site since March so I now know far more than I ever needed to about the Waveterm We had it and the PPG2.2 on display at an event last weekend so once word got around that I could recreate floppies for it I suddenly had people from the Fairlight community talking to me too.

    I spent all last night testing and checking jumpers on different drives and yes, for a YD380 to move from Waveterm to PC I just needed to jumper the 'HS' pins ('head select'?) - I checked another machine I had on the bench (Ferranti Advance86) and the YD380 wouldn't work in that because it only used a double density floppy controller. I noticed though that 'HS' was jumpered along with DS1 so I installed it in my imaging PC with those jumpers set and it worked first time

    I also found this which is a long read but it teaches you more than you'll ever need to know about floppy drives and formats.

    http://www.retrotechnology.com/herbs_stuff/drive.html

    Next: an 8" drive with an FDADAP 50 pin adapter.

    Cheers
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

  5. #5
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    There was also a modification of the Shugart SA400 interface used by Microopolis--it was minor, but changed the position of some of the drive select pins.

  6. #6

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    Hopefully nothing that affects a single drive. I need to check what my 8" drives are, they're in a CPT 8500 word processor and in unknown condition since the machine itself doesn't work.
    www.binarydinosaurs.co.uk - UK home computer history
    Where RIFA capacitors come to die
    facebook.com/binarydinosaurs

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