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5150 Tandon full height fdd, cable and terminator?

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    5150 Tandon full height fdd, cable and terminator?

    5150 Tandon full height fdd, cable and terminator?

    Trying to find which configuration for the fdd drive, which connector and do I use and do I use a terminator?

    Single drive in system

    #2
    It all sort of depends on the cable you are using. IBM types typically use the Twisted cable (Conductors 10-16 Twisted) and
    the Floppy Attaching Connectors are one in middle of cable (Drive 1) and one Connector after the Twisted Conductors (Drive 0).
    But, the Drive on the END of the cable has twisted Conductors so it also must be Strapped for DS=1 in a DS{0..3} configuration.
    The Terminator is always installed In the last floppy installed on the end of the cable.


    Larry

    floppy_crossover_cable_wiring.jpg

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      #3
      See the 'Cable and Termination' section of [here].

      The Tandon TM100-2's terminator is pictured at [here] and described at [here].

      Comment


        #4
        5.25-jumpers.pdf (cbmstuff.com)

        found this

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          #5
          With two drives and no terminator, system boots from fdd on end socket after the twist. Little leg broke off terminator.

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            #6
            In the very short runs of cable, it really doesn't matter which floppy has the terminator (pullup resistors) attached. The couple of inches between floppies is extremely unlikely to result in signal reflectios. Remember that the original SA800 spec this was based on envisioned meters between drive and controller. The old traditional value of the termination pullups is usually 150 ohms to Vcc.

            Eventually, with the advent of 3.5" drives, reality set in. The value of termination resistance was greatly increased (saves power) to a couple of K and was enabled on all drives. The reality of modern computers no longer meant long distances between controller and drive. I do have some very old 720K 3.5" drives that do have the termination packs in sockets, however.

            Bottom line is that you need the pullup somewhere, as the specs still say that outputs are driven with open collector/drain drivers. Used to be that 7438 was the go-to IC for that purpose, but in fact, a 74LS06 or LS07 (or its CMOS relatives) is sufficient nowadays.

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              #7
              I used the info here minuszerodegrees.net

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                #8
                I've installed an XT-IDE adapter with a CF card. Using a 5.25" and a 3.5" FDD, I can boot off either drive through the XT-IDE adapter.

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