Power Supply for Asus P5AD2 Motherboard?

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

The Asus P5AD2 Deluxe motherboard uses a 24-pin ATX power connector. There
are very few power supplies available that support this new ATX 12V Version
2.0 format. Is it safe to use a standard 20-pin power supply with this
motherboard? The manual is somewhat vague in regard to this issue, and I'm
looking for a definitive answer.

Thanks.
5 answers Last reply
More about power supply asus p5ad2 motherboard
  1. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    On Sun, 19 Sep 2004 03:34:05 GMT, "X Offender"
    <nospamplease@earthlink.net> wrote:

    > The Asus P5AD2 Deluxe motherboard uses a 24-pin ATX power connector.
    > There are very few power supplies available that support this new
    > ATX 12V Version 2.0 format.

    http://www.antec-inc.com/ec/productDetails.php?ProdID=07553

    http://www.antec-inc.com/ec/productDetails.php?ProdID=05480
  2. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    "Ken" <___ken3@telia.com> wrote in message
    news:shcqk097ru26m4vvri28jsa2tp5g793j7p@4ax.com...
    > http://www.antec-inc.com/ec/productDetails.php?ProdID=07553
    >
    > http://www.antec-inc.com/ec/productDetails.php?ProdID=05480

    Thanks, Ken. I do know that they exist, and I was actually looking at the
    Antec NeoPower, but I already own a 500W power supply that I like better,
    and I'd prefer to use it rather than purchasing a new one, if possible. The
    motherboard manual says that use of a 20-pin power supply is "not
    recommended," though it can be done. Every review of the board that I've
    read, though, says that using a standard power supply works fine, and that
    the board is fully backward-compatible with the 20-pin power supplies. I'm
    just trying to ascertain whether it's a good idea or not. I need the new
    machine I'm building with this board to be reliable.
  3. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    In article <N673d.6533$mb6.4923@newsread3.news.atl.earthlink.net>, "X
    Offender" <nospamplease@earthlink.net> wrote:

    > The Asus P5AD2 Deluxe motherboard uses a 24-pin ATX power connector. There
    > are very few power supplies available that support this new ATX 12V Version
    > 2.0 format. Is it safe to use a standard 20-pin power supply with this
    > motherboard? The manual is somewhat vague in regard to this issue, and I'm
    > looking for a definitive answer.
    >
    > Thanks.

    The difference between connectors is in the ability to deliver current
    to the load, the ampere capacity. The Minifit Jr connector is rated
    for 6 amps per pin, and that figure is used to derive the following.

    If you compare the 20 pin connector to the 24 they show in the
    manual, the 24 has an extra +3.3, +5.0, +12, and GND pin. Pin 1
    of the 24 pin connector, I think, is in the lower left hand corner.
    Pin 1 of the 20 pin connector should plug in there. The top four
    pins are the "extra" ones.

    The extra pins would be worth 6 amps a piece. For +3.3V, it boosts
    the limit from 18amps to 24amps. For +5.0V, it boosts the limit from
    24amps to 30amps. For +12V, it boosts the limit from 6amps to
    12amps (from the ATX connector, plus it can draw another 2x8=16amps
    from the 2x2 connector). Those are the amounts of current that
    can flow from the PSU to the motherboard, without damaging the ATX
    power connector. Generally, the 2x2 connector is used only for the
    processor, whereas the single +12V pin on the ATX 20 pin is used
    to handle fan headers etc.

    On the load side, the new motherboards aren't much different from
    older motherboards. PCI Express is a bit different, and especially
    the video card slot could place new demands on things.

    I found an Intel slide set, and it lists the PCI-E video card slot
    power limits. These limits are based on the PCI-E connector and
    how much current can flow through the pins of the video card.

    +12V 5.5A (max)
    +3.3V 3.0A (max)
    3.3Vaux 0.38A (max) [ likely regulated down from +5VSB ]
    (Card may draw a total of 75W. Ordinary 1x PCI-E cards are allowed
    up to 25W.)

    If you had a video card that draws as much power as it can from
    +12V via the edge connector of the video card, and you used the ATX
    20 pin connector, the card can draw 5.5A and the single +12V pin
    on the ATX 20 pin is rated for 6A. Asus usually powers the fan
    headers from this +12V pin, so if three fans drew an amp or so,
    the total draw would be 6.5A.

    PSU --+---- single +12V pin ------+-----+-----+-----+
    | MiniFit Jr 6A per | | | |
    | pin limit Fan Fan Fan PCI-E Video
    | 0.33A 0.33A 0.33A 5.5A
    |
    2x2 +---> Up to 16A for Vcore.
    12V | 115W Prescott draws
    conn. +---> (115W/12V)*(1/0.9)=10.6A

    If you buy a video card, and it uses an aux connector on one corner
    of the video card, that connector will provide the extra current the
    card requires. But, the trouble is, the PCI Express video cards I've
    looked at so far, don't have an auxiliary connector for power,
    which means it is all coming through the edge card.

    This article measures power consumption of current generation cards.
    This is for an AGP card, but the PCI-e will just use a hot bridge
    chip to get to PCI-e country. The 6800 is measured at 72W at full
    load.

    http://www.xbitlabs.com/articles/video/display/ati-vs-nv-power_10.html

    The current measurement is here. 12V@4.62A. With the three fans on
    the same +12V pin, the total current of 5.62A is just under the 6A
    limit. You could help things a bit by running the fans off Molex
    disk drive connectors, and just route the tacho signal to the mobo
    fan headers.

    http://www.xbitlabs.com/articles/video/display/ati-vs-nv-power_2.html
    http://www.xbitlabs.com/misc/picture/?src=/images/video/ati-vs-nv-power/6800u_table-b.gif&1=1

    Any 1x PCI-E cards that you plug into the other slots, will
    be drawing next to no power (like 1W for a typical function), so
    they don't even enter into the equation. It would take a complex
    function, like say an embedded computer on a board, to draw
    enough power to be a concern. Any PCI-e card consisting of a
    single chip on board (Ethernet, cheap sound card, Firewire card,
    USB card) will draw around 1W or less.

    Here is an example of a PCI Express video card that has two
    Molex drive connectors for power. A card like this means you
    can use the ATX 20 pin without worrying. It means the designer
    is running the switchers from the Molex connectors.

    http://www.tweakers.net/nieuws/29357

    But the other PCI Express video cards I've looked at, don't use
    an Aux connector, so the 5.62A of 6A test case above remains as
    the closest to heating up the single +12V pin on an ATX 20 pin
    connector.

    In the description above, notice how easy it is to draw more
    than the 12V@15A recommendation for a basic system. At 10.6A
    for high end processor, 4.62A video, 1A fans, 0.5A per drive,
    18A is the starting number, and a couple more amps for margin
    would help. Since the processor and disk drive currents are
    flowing through other pins and cables from the PSU, there is
    no danger from those loads.

    It is difficult to do a similar analysis for the other supplies,
    except to use an Intel motherboard power spec. This spec is
    for the Intel D925XCV, and table 37 is on page 85.

    ftp://download.intel.com/design/motherbd/cv/C6859701.pdf

    Table 37. DC Loading Characteristics
    DC Current at:
    Mode DC Power +3.3V +5V +12V -12V +5VSB
    Minimum loading 200.00W 3.30A 10.00A 9.00A 0.03A 0.80A
    Maximum loading 300.00W 6.00A 14.00A 16.00A 0.10A 1.40A

    The +3.3V and +5V currents are low, compared to the 18A
    and 24A limits of the ATX 20 pin connector, so those
    shouldn't be a problem. The Intel manual says part of that
    +5V allocation, is to power imaginary PCI-e cards drawing
    an average of 2A per slot.

    So, under some circumstances, the +12V pin on the ATX 20 pin
    connector is running close to its limit, and that is
    where the "you can do it, but not recommended" comes from.

    HTH,
    Paul
  4. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    "Paul" <nospam@needed.com> wrote in message
    news:nospam-1909041015310001@192.168.1.177...
    > ...
    >
    > HTH,
    > Paul

    Wow. Thank you so much for taking the time to write such a clear and
    detailed explanation. That helps a great deal, as I know next to nothing
    about these power issues.

    The video card I'll be using is the PCI Express Gigabyte Radeon X600 XT
    (model # GV-RX60X128V). It does not utilize an auxiliary power connector. I
    have no idea what kind of power consumption to expect from this card. I'll
    also be running two 120 mm case fans. I won't be installing any other cards,
    as this motherboard has virtually everything built in (I'll be using onboard
    sound and networking).

    The specs of my power supply are as follows:

    DC Output Load Max
    +3.3V 28A
    +5V 30A
    +12V 34A
    -5V 0.3A
    -12V 0.8A
    +5VSB 2A

    +3.3V & +5V Combined Load: 200W
    +3.3V, +5V, & +12V Combined Load: 480W
    Total Max Power Output: 500W

    Here's a list of all of the other components that will be drawing power in
    my system, if it matters:

    CPU: Intel LGA775 P4 530 3.0 GHz with stock heatsink/fan
    Hard Drives: two SATA 250 GB 7200 RPM, one IDE 80 GB 7200RPM
    Optical Drives: 16x dual layer DVD+/-RW, 52x32x52x CD-RW
    Floppy Drive
    a few cold cathode lights

    I would think that I'll probably be okay with that power supply for now,
    even though the +12V pin may come close to being maxed out (mostly depends
    on how much power the video card actually draws, yes?). Bottom line: I just
    want to know that I won't damage anything by running with the current power
    supply for a while. Would you advise against it, or should I be okay until
    I'm able to upgrade to a 24-pin ATX 12V 2.0 model?
  5. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    In article <XOl3d.6992$mb6.1587@newsread3.news.atl.earthlink.net>, "X
    Offender" <nospamplease@earthlink.net> wrote:

    > "Paul" <nospam@needed.com> wrote in message
    > news:nospam-1909041015310001@192.168.1.177...
    > > ...
    > >
    > > HTH,
    > > Paul
    >
    > Wow. Thank you so much for taking the time to write such a clear and
    > detailed explanation. That helps a great deal, as I know next to nothing
    > about these power issues.
    >
    > The video card I'll be using is the PCI Express Gigabyte Radeon X600 XT
    > (model # GV-RX60X128V). It does not utilize an auxiliary power connector. I
    > have no idea what kind of power consumption to expect from this card. I'll
    > also be running two 120 mm case fans. I won't be installing any other cards,
    > as this motherboard has virtually everything built in (I'll be using onboard
    > sound and networking).
    >
    > The specs of my power supply are as follows:
    >
    > DC Output Load Max
    > +3.3V 28A
    > +5V 30A
    > +12V 34A
    > -5V 0.3A
    > -12V 0.8A
    > +5VSB 2A
    >
    > +3.3V & +5V Combined Load: 200W
    > +3.3V, +5V, & +12V Combined Load: 480W
    > Total Max Power Output: 500W
    >
    > Here's a list of all of the other components that will be drawing power in
    > my system, if it matters:
    >
    > CPU: Intel LGA775 P4 530 3.0 GHz with stock heatsink/fan
    > Hard Drives: two SATA 250 GB 7200 RPM, one IDE 80 GB 7200RPM
    > Optical Drives: 16x dual layer DVD+/-RW, 52x32x52x CD-RW
    > Floppy Drive
    > a few cold cathode lights
    >
    > I would think that I'll probably be okay with that power supply for now,
    > even though the +12V pin may come close to being maxed out (mostly depends
    > on how much power the video card actually draws, yes?). Bottom line: I just
    > want to know that I won't damage anything by running with the current power
    > supply for a while. Would you advise against it, or should I be okay until
    > I'm able to upgrade to a 24-pin ATX 12V 2.0 model?

    The two best articles on measuring video card power are here:

    http://www.xbitlabs.com/articles/video/display/ati-vs-nv-power_2.html
    http://www.xbitlabs.com/articles/video/display/ati-powercons.html

    An X800XT draws 3.5A from +12V, and I would expect the X600XT to
    be the same or less. I don't expect a problem in your case.

    And your +12V current rating of 34A seems to be a lot more than
    the 15-18A the system might be drawing under load.

    HTH,
    Paul
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