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Thread: ATX board power??

  1. #1
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    ATX board power??

    I have a Epia Via 800 Mini-ITX board which requires an ATX power source.

    ATX has +/- 12V, +/- 5V, and +3.3V

    Now can I use an AT power source?
    The AT power source doesn't have the 3.3V like the ATX, BUT does the board need this?
    If not I rather get a cheaper AT power supply then an more expensive ATX psu.

  2. #2
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    Re: ATX board power??

    Originally posted by Alphared
    I have a Epia Via 800 Mini-ITX board which requires an ATX power source.

    ATX has +/- 12V, +/- 5V, and +3.3V

    Now can I use an AT power source?
    The AT power source doesn't have the 3.3V like the ATX, BUT does the board need this?
    If not I rather get a cheaper AT power supply then an more expensive ATX psu.
    The connectors for the motherboard are totaly diferent. So, I would say this would not work. Plus, you are using an EPIA motherboard...It doesn't require much power and you could get an 90W eMachine PSU for $20. I would say thats on par with the AT PSU. Check eBay out. I got a 150W PSU for $1.50 once. I know they have cheap PSU there.
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  3. #3
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    I'm pretty sure he's asking about dc-dc supplys. Read the side of the RAM you have for it. It'll say 3.3V. So unless you do don't intend on using any RAM, better get a supply that has the 3.3V.

    MIKE

  4. #4
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    yeah, i was talking about dc-dc psu ($150 and up) I've seen on this board a AT-ATX converter, would that work?

  5. #5
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    Originally posted by Alphared
    yeah, i was talking about dc-dc psu ($150 and up) I've seen on this board a AT-ATX converter, would that work?
    As good as they look, these don't exist. Its just an adapter from one type plug to another. It does away with the 3.3V altogether. Meaning you will definately lose soft power, and most likely, it just won't work. I almost tried it, never wanted to risk my new epia.

    MIKE

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    Maximum Bitrate CrazyLittle's Avatar
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    3.3v is only used for the RAM/AGP and some PCI cards, and even then I think somebody here found that some mobos will pull that current from the 5v rail.

    here's an excellent link on the purpose of that 3.3v rail, as well as power consumption for typical components:
    http://www.thetechboard.com/tutorials/atx.php

  7. #7
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    Wasn't there someone on here that was willing to build a at>atx adapter that pulled from the 12vdc rail and turned it into 3.3vdc?
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  8. #8
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    Originally posted by CrazyLittle
    3.3v is only used for the RAM/AGP and some PCI cards, and even then I think somebody here found that some mobos will pull that current from the 5v rail.

    here's an excellent link on the purpose of that 3.3v rail, as well as power consumption for typical components:
    http://www.thetechboard.com/tutorials/atx.php
    Yep. Thats definately a good source.

    People have talked about a true converter, hopefully pulling from the 5V rail, why would you want to waste the extra voltage from a 12V? I don't see why you couldn't use a solid voltage divider for this... the 5V is regulated, theres nothing more to it. There has been a lot of talk on ways to do this though...

    Use a 250 and 95 ohm resistor. take the 3.3V off the 95 ohm.
    You'll get 34.8mA and 302.8mW

  9. #9
    FLAC MP3DUB's Avatar
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    Originally posted by selfentitled
    Yep. Thats definately a good source.

    People have talked about a true converter, hopefully pulling from the 5V rail, why would you want to waste the extra voltage from a 12V? I don't see why you couldn't use a solid voltage divider for this... the 5V is regulated, theres nothing more to it. There has been a lot of talk on ways to do this though...

    Use a 250 and 95 ohm resistor. take the 3.3V off the 95 ohm.
    You'll get 34.8mA and 302.8mW
    I was under the impression that the 12vdc line often has the most unsed amperage, as most signaling is 5vdc, leaving the 12vdc to spin motors.
    -Nick

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  10. #10
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    Ah. good point. Overlooked. I reall don't see it mattering.. RAM does not take much current.

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