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copper traces to nowhere on MSI desktop motherboard

Discussion in 'Electronic Design' started by Bob Boblaw, Dec 10, 2012.

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  1. Bob Boblaw

    Bob Boblaw Guest

    I have an MSI Z68A-G43(G3) desktop motherboard with an Asmedia ASM1083 PCI-E to PCI bridge chip. That chip seems to be designed to connect to 2 thin serpentine copper traces, each about 2" long, that go nowhere. On this particular motherboard they're not used at all because the jumpers that normally connect to the chip (labeled SIM1 and SIM2 in the picture below) aren't installed, and neither are the header pins for the jumpers. Notice that each serpentine trace has 2 traces adjacent to it that follow it, only they're designed to not be connected to anything at either end.

    Asmedia hasn't replied about their chip, and I can't find a datasheet or pinout, but does anybody know the purpose of unconnected serpentine traces like these?

    http://imageshack.us/photo/my-images/22/signalstonowhere.jpg/
     
  2. Joerg

    Joerg Guest


    Sometimes those are used to generate very short pulses, in lieu of a
    chunk of coax. But hard to say without a schematic.
     
  3. I would guess it's for testing the PCB controlled impedance (using a
    microstrip line test coupon) by way of the missing 'SIM2' header.
    Nothing to do with the chip.
     
  4. Guest

    Funny looking transformer?


    Mark L. Fergerson
     
  5. Sjouke Burry

    Sjouke Burry Guest

    That looks like a nice delay line,providing you with a reflected pulse
    for every transmitted pulse.
    Now start thinking about how to use that pulse.....
    (oh, and make the transmitted pulse short enough to not interfere
    with the returning echo pulse).
     
  6. tm

    tm Guest

    More likely it is there to measure the properties of the PC board. Maybe for
    QC?

    tm
     
  7. Joerg

    Joerg Guest

    Or a secret antenna? Big brother watching? Oh-oh ... :)
     
  8. The PCI buss is based on reflected signals.......

    Maybe some kind of sanity check.

    Cheers
     
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