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Thread: [H81 ProBTC] specialist pci 1x power but safe for 60w through riser cable?

  1. #1
    Join Date
    Mar 2014

    Default [H81 ProBTC] specialist pci 1x power but safe for 60w through riser cable?

    Simple burning question-

    Using 750ti's which many don't have a external power connector drawing all power usage from the MOBO.
    The TDPs of the cards are low but will need to be up to 60-65 Watts for OC.

    I have the H81 ProBTC which I believe can provide those 65 Watts even through the pci 1x ports correct?
    I am now wandering if the 1x Riser cables I have (like:Pci-e 1x Riser | eBay) can handle 65 watts passing through? I'm hearing things about 5 amps and melting so I need to ask...

    If it isn't safe there wasn't much cause to provide extra power to these 1x slots by asrock. Is there a difference between these ribbon cables and the USB style ones on the market in regards to Wattage tolerance (Fixable PCI-E 16X to 1X Adapter USB 3.0 Riser Cable w/ Molex 4P Power Connector | eBay)

    Encase anyone is wandering to help with my rig, I'm trying to run 6 x 750ti cards, at around 60w each. I know this motherboard can provide the power in theory I'm just worried about unavoidably using the riser cables and their safe limit.

    Any help would be massively appreciated just cannot find any info on it. Cheers!

  2. #2
    Join Date
    Nov 2012

    Default Re: [H81 ProBTC] specialist pci 1x power but safe for 60w through riser cable?

    Not to dissuade you from persisting for a reply but ASRock has as of earlier this year set up a Mining Only Tech Forum for support of their BTC motherboards..

    ASRock's Bitcoin Boss Forum

    Be forewarned, you'll need to use your browsers translator.
    #1 - Please, when seeking help, enter the make and model of ALL parts that your system is comprised of in your Signature, or at least the model #'s in your System Specs, then "Save' it.
    ____If you are overclocking, underclocking, or undervolting any parts, informing us of this and their values would prove beneficial in helping you.

    #2 - Consider your PSU to be the foundation from which all else is built upon. Anything built upon a weak foundation is poorly built.

  3. #3
    parsec's Avatar
    parsec is offline Senior Member
    Join Date
    Jun 2012
    Third stone from the sun

    Default Re: [H81 ProBTC] specialist pci 1x power but safe for 60w through riser cable?

    The good news is all the power connections on a PCI-E lane of any type are found at the very front of the slot, so a PCI-E x 1 card will get all the power available from the slot. The rest of the pins on an x4 to x16 slot/card are for data.

    [H81 ProBTC] specialist pci 1x power but safe for 60w through riser cable?-pciex1-pin-jpg

    See for yourself here, scroll down to find links to x4 to x16 pin outs.

    Serial PCI Express Bus 1x PinOut and PCIe pin out Signal Names

    Note that a PCI-E x 16 slot has pin #3 on side B as an additional +12V power pin that is not used on any other PCI-E slot.

    Given what I can find, each +12V pin is capable of 1.25A, so four of them in a PCI-E x 1 slot is 60 Watts (5 Amps). That ignores any power draw through the 3.3V pins.

    The extra +12v pin on a PCI-E x 16 slot allows for 75 Watts. What ASRock did with the PCI-E x 1 lanes on this board I don't know, meaning are they 60W or 75W, the latter being non-standard.

    You believe the PCI-E x 1 slots on your board can provide 65 Watts, because... ?

    The extra power connectors on this board are there to provide power to the five PCI-E x 1 lanes, plus the single PCI-E x 16 lane. Five x1 lanes @ 60W each is 300W, plus 75W for the x16 lane. Standard x1 lanes for non-video card use have a 10W power spec, with a max of 25W. This means that the standard power delivery to a non-BTC board is less than the 300W - 375W that should be available on the BTC board. My point is the extra power connectors are not provided to provide more than 60W per x1 port, but to provide 60W to five x1 ports.

    If you can find different specs in the manual, etc, then fine, otherwise the standard specs apply.

    I wonder about the power capability of those risers too, they don't have any specs.

    A 750Ti using 65W would be fine in an x16 slot, but an x1 slot is borderline IMO.

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