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Re: [midatlanticretro] Acquired a PDP-8/E

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  • Dave McGuire
    ... Excellent! That s a great start. I see Dave G has weighed in on the voltages...his advice is exactly what I would ve given. We re on the right track
    Message 1 of 91 , May 21, 2013
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      On 05/21/2013 10:55 AM, Kyle Owen wrote:
      > So all in all, I have powered the supply on and verified that all of the
      > voltages appear correct (still want to check on this V2 bus, but I think
      > it's a second 5V line from the looks of it), reinstalled the boards,
      > powered on the machine, and verified that it does work! 11 of the blue
      > incandescent bulbs have burned out, but the address does count when
      > examining or depositing.

      Excellent! That's a great start. I see Dave G has weighed in on the
      voltages...his advice is exactly what I would've given. We're on the
      right track with this machine.

      > Just wondering, why are the bits numbered in seemingly reverse order?
      > Bit 11 is the 1s bit, and bit 0 is the 2k bit. Seems very odd compared
      > to every other machine I've played with.

      Well keep in mind that the PDP-8 (though not the 8/e) hit the streets
      in 1965. The de-facto standard of numbering the switches with their
      binary "2^n" weight had not really taken hold much at that time.

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
    • Dave McGuire
      ... OS/8 needs a random-access storage device; paper tape won t do it. Magnetic tape drives are *physically* sequential-access, of course, but the TU56 (for
      Message 91 of 91 , Jun 6, 2013
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        On 06/06/2013 12:54 PM, Kyle Owen wrote:
        > That looks like a nice product, but yes, it's certainly expensive. I've got
        > some FPGA background myself, along with several different microcontrollers,
        > so I may see about creating something that will work with my high-speed paper
        > tape interface. That could be considered an OS/8 storage device, yes?

        OS/8 needs a random-access storage device; paper tape won't do it.
        Magnetic tape drives are *physically* sequential-access, of course, but the
        TU56 (for example) is logically a random-access, block-oriented device. (with
        highly variable latency ;))

        > I would
        > have no idea how to go about writing a driver for it yet, but perhaps it'd be
        > in my best interest to start reading up on the commands for the card and then
        > learn more about OS/8. Do you have any suggestions on recommended reading for
        > this?

        If this was a generally-directed question...The book you want for "most
        things OS/8" is the "OS/8 Handbook". It is excellent. Try to find a paper
        copy if you can, but it's available in PDF on bitsavers:

        http://bitsavers.trailing-edge.com/pdf/dec/pdp8/os8/OS8_Handbook_Apr1974.pdf

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
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