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Thread: Clearing out some IBM 4869-002 External drive boxes

  1. #31
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    Quote Originally Posted by Unknown_K View Post
    For some reason I was under the impression the old towers had external floppy ports, must just be serial and parallel. Anyway I have an external IBM drive with the ISA version of the IBM card that I used with the PS/2 model 30 286. The drive itself has the asterisk on the faceplate.
    That'd be the 360KB diskette drive, with the asterisk. You could probably cater for that with DOS DRIVPARM, if you could hook it up to the FDC somehow, assuming you only have one other diskette drive.

  2. #32

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    These will just plug in to the 5150/5160 FDC and work? DOS configuration notwithstanding, I just mean is the pinout the same?

  3. #33
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    Not quite, but almost. See my blog post on this.

  4. #34

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    Quote Originally Posted by Chuck(G) View Post
    Not quite, but almost. See my blog post on this.
    your pics don't show pin 1, but it appears you're just swapping DS0 and DS3? so in theory you could just change the DS jumper on the drive and leave the cable alone right?

  5. #35
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    Could be--it's been years since I wrote the blog post. Not all PC drives feature drive select jumpers.

  6. #36

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    I was looking at the Shugart pinout which has DS3 on pin 6 and DS0 on pin 10. IBM used pin 10 for Motor ON (drive A) and pin 6 for ? in the internal PC cabling, so apparently they moved motor on to pin 6 on this enclosure. Odd

  7. #37
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    IBM needed individual drive motor control, so they repurposed DS0 and DS2.

    So MOTOR ON on a flat cable is pin 16 and drive select is DS1 on pin 12.
    Now take the bundle (with ground returns on 10 through 16) and twist the leads such that pin 10 and 16 are exchanged and pins 12 and 14 are similarly exchange. What you sacrifice is DS0 and DS2. But now both drives are identically jumpered and you get independent drive motor control.

    Pins 6 and 4 (DS3 and INUSE) aren't used in the PC floppy interface. I've got a couple of SCSI and ESDI controller cards that uses these as the MOTOR and SELECT for a third drive (the "twist" in this case is a little weird), but it works.

    I've got a DTC ESDI card that also has a jumper that allows 4 floppy drives in the "all flat" DS0-DS3 configuration. When any floppy motor is enabled, all motors are.

  8. #38

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    Quote Originally Posted by Chuck(G) View Post
    IBM needed individual drive motor control, so they repurposed DS0 and DS2.

    So MOTOR ON on a flat cable is pin 16 and drive select is DS1 on pin 12.
    Now take the bundle (with ground returns on 10 through 16) and twist the leads such that pin 10 and 16 are exchanged and pins 12 and 14 are similarly exchange. What you sacrifice is DS0 and DS2. But now both drives are identically jumpered and you get independent drive motor control.

    Pins 6 and 4 (DS3 and INUSE) aren't used in the PC floppy interface. I've got a couple of SCSI and ESDI controller cards that uses these as the MOTOR and SELECT for a third drive (the "twist" in this case is a little weird), but it works.

    I've got a DTC ESDI card that also has a jumper that allows 4 floppy drives in the "all flat" DS0-DS3 configuration. When any floppy motor is enabled, all motors are.
    Yeah that all makes sense, but what I can't quite wrap my head around is that in the blog pictures you appear to be swapping Pin 6 and Pin 10. Neither one of those should matter for an "IBM" style cable arrangement since the drive expects "motor on" on pin 16 and drive select on pin 12 as you said.

  9. #39
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    Again, I don't recall, only that it works (I've got about 6 different drives set up that way, including one CF2).

  10. #40

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    Quote Originally Posted by Chuck(G) View Post
    Again, I don't recall, only that it works (I've got about 6 different drives set up that way, including one CF2).
    is it possible that change was necessary for the OEM disk drive that was included in the 4869 and not specifically the enclosure itself?

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