9NPA+ Boot Problem

Discussion in 'Epox' started by jmbowles, Jan 18, 2009.

  1. jmbowles

    jmbowles Guest

    Hello all,

    My friend has an EP-9NPA+ motherboard. He is currently running with
    an nVidia 6600GT video card. When I went to upgrade the card to a
    9600GT, I got a C1 error on the board. My first thought was not
    enough power. He currently has an Antec SL-350S power supply. I have
    an Antec SP-400 power supply in my PC, so I swapped that out with his
    PS to test. Still a no go. I put his old 6600GT card back in, and
    try to boot again with my SP-400 power supply. I get the blue LED on
    the board to light up, but when I hit the PC power switch nothing
    happens. When I put his SL-350S power supply back in, it powers on

    Now here's the weird part. When I plug in the old SL-350S power
    supply and flip the power supply switch on, the fans, blue LED, and
    LED displays on the board jump for a second which gives me the
    impression they have juice. When I plug in the newer SP-400 power
    supply and flip the switch, that doesn't happen (and the board won't
    power on). The SP-400 still works with my PC, so it isn't dead.

    My first problem is figuring out why my power supply won't power the
    board. I don't want to upgrade his power supply only to find that the
    new one won't turn the PC on for some strange reason. Does anyone
    have any idea what might be going on?
    jmbowles, Jan 18, 2009
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  2. jmbowles

    jmbowles Guest

    One additional thing I've noticed with this. The SL-350S power supply
    my friend has only has a 20-pin connector. The SP-400 I'm swapping
    from my PC has a 24-pin connector. Is there any BIOS setting or other
    board issue that could keep the board from even trying to boot because
    of the power supply change?
    jmbowles, Jan 18, 2009
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  3. jmbowles

    Paul Guest

    The BIOS doesn't monitor the ATX power connector as such. Logic
    circuits are checking for some conditions to be met though, before
    the BIOS is allowed to run.

    These specs discuss the two generations of power supplies.

    http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf (page 30)

    http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf (page 37)

    Note that pin 1 of the 24 pin, goes to pin 1 of the 20 pin connector.
    Some 24 pin connectors make this easy, by allowing the end four
    pins to be hinged out of the way. The "extra" four pins are
    detachable. If the connector happens to be the non-detachable
    version, the four left over pins on one end of the connector
    can be left dangling in space. They're redundant and aren't adding
    any new voltage values. They're just more pins to carry more
    current (amperes).

    When the motherboard wants to turn on the power supply, it grounds
    the PS_ON# signal. The PS_ON# is held at 5V normally, via a pullup
    resistor. A driver chip or transistor on the motherboard, is used
    to pull the signal to ground level (logic 0), which tells the
    power supply to turn on.

    The PWR_OK goes to a 5V level, when the power supply has stabilized.
    That is how the motherboard knows the power supply is ready.
    The PWR_OK signal then goes through some logic chips, which
    check the levels of any locally regulated voltages. When
    the motherboard finds all voltages stable (external and internal),
    and the reset interval is completed, the motherboard can start.
    But PWK_OK only happens when the PS_ON# thing kicks
    things off. (See figure 7 of the second document above,
    for a timing diagram of the signals.)

    What should happen, when the switch on the back of the
    supply is turned on, is the motherboard should not be
    glitching the PS_ON# and causing other rails on the
    supply to glitch in response. The motherboard should
    quietly wait until the user presses the front POWER
    button, before the PS_ON# signal is fed to the power
    supply. And the processor plus BIOS cannot boot the
    board, unless "PWR_OK and friends" are happy.

    I resisted answering your post when it first showed up,
    because I was going to present a theory that the issue
    had to do with -5V. But then I discovered that the
    SL350S doesn't have -5V on it, so I could not explain
    the issue as being something to do with a missing
    -5V on the new supply. The old supply is missing
    -5V anyway. You'll notice on page 30 of the first
    document above, pin 18 is marked "reserved" and
    that is the place where the -5V was removed from
    the supply spec. The corresponding pin on the
    24 pin connector will also be marked as reserved,
    for the same reason.

    There are a few old motherboards that won't run
    unless -5V is present. And thus, when a user
    has an old power supply fail, and then they
    substitute a new supply, the missing -5V pin
    trips them up. It isn't supposed to happen that
    way, but apparently there are some motherboards
    that have a dependency on -5V.

    Anyway, I don't have anything really to add about
    your original problem description. (No strong
    suspicions.) It would be nice if the Epox documentation
    had a table of POST codes, so you could
    find out what "C1" is.

    The 9600GT is a PCI Express revision 2 card, while
    the motherboard is likely revision 1. In the case
    of the 8800GT (G92), another Nvidia product, there
    was an issue with the card failing to negotiate
    PCI Express speed properly with revision 1 motherboards.
    A workaround was to get a special version of the video
    BIOS and reflash the card so that it would only run in
    revision 1 mode. I'm not aware of that mistake
    being made by Nvidia, other than on the 8800GT.
    Perhaps you can try some Google searches, and
    see if the 9600GT offered by some video card
    manufacturers, may have a similar video BIOS
    issue. (Like, maybe some Newegg reviews might
    have evidence of a problem.)

    Oh. Another dumb question. Does the 9600GT have
    a 2x3 power connector on the end of the card ?
    Is that plugged in ? If it isn't powered, you
    may need a Molex 1x4 to PCI Express 2x3 adapter
    cable, to give the card some power.

    This picture highlights a typical 9600GT power connector.


    This is the adapter you'd try, if the power supply
    doesn't have a 2x3.



    Paul, Jan 18, 2009
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