help me understand 12V rails beh!!!

[negative_black03]

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ok. heres the thing, i bought a PSU with FOUR +12V rails @20 amps each, pero its also indicated that it has a combined 70 Amps.

i quess my question is.. with the Vcard im using which requires two 6pin power connectors , am i only getting 40 Amps for the card since it uses two 6pin power connectors?

[fineupgrades]

Your motherboard supplies the majority of power needed by your VC through the PCI-E slot itself. 6-pin or 6+2-pin PCI-E power connectors on the cards are used to supply the remainder of the graphics card’s power requirement.

[EarlZ]

ok. heres the thing, i bought a PSU with FOUR +12V rails @20 amps each, pero its also indicated that it has a combined 70 Amps.

i quess my question is.. with the Vcard im using which requires two 6pin power connectors , am i only getting 40 Amps for the card since it uses two 6pin power connectors?

Yes you are giving it 20 or 40 amps depending on how the rail distribution is done on your PSU, if for example for every 6pin PEG cable, say its assigned to different rails this means that your videocard can have access to as high as 40amps, if both connectors sit on the same rail then it will only get 20amps.

IIRC modern day videocards still use upto 18amps on a dedicated rail so you need not worry about it that much.

Your motherboard supplies the majority of power needed by your VC through the PCI-E slot itself.

Depends on the graphics card, the PCIE-16x slot can only offer 75watts as per spec, same with the 6pin connectors at 75watts each, 8pins offer 150watts.

Design wise, ATI/nVidia has been making cards to draw from the 6/8pin primarily and then on to the PCIe slot, so say if we have a 300watt GPU with dual 8pins, the card will probably draw 140watts per 8pin and 20watts on the PCI-e slot.

[werty]

disregard that 20Amps per rail(12V1, 12V2 etc), i think this limit has been removed from the ATX 2.1 specification(or was it already atx 2.2V?)....

each 6-pin PCIE-connector is supposed to pull about 75watts(90watts for 8-pin i think), and the pcie slot can also give 75watts max.

[orlyboy78]

nose bleed ko ana da....hehehhe

[EarlZ]

As stated, 150watts per 8pin. PCIE 2.x spec limits the total power draw to 300watts.

[negative_black03]

thanks EarlZ. i think im getting the hang of this 12V rails thinggy...

[EarlZ]

NP, if you have other questions feel free to ask.. a lot of enthusiasts here can give you info ( or even overload you with info hehe )