# 4pin molex plug near pcie on motherboard



## welly321 (May 19, 2009)

Is this molex connection on the motherboard (specifically foxconn a79a-s) needed if  I am using crossfire. I am currently running it without it plugged in, and it works fine. It seriously messes up my airflow to plug it in but i dont want to ruin my video cards. Is this connection a must when running crossfire?


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## CDdude55 (May 19, 2009)

My 680i board is similar, even tho they(generally the manuals) say to plug it in if using SLI/Crossfire its not absolutly needed, if you know your cards are getting the sufficent amount of power it shouldn't be a problem at all running without it.


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## largon (May 19, 2009)

*Short answer:*
No. It's not required.

*Long answer:* 
4pin molex has 1×12V pin, 2×ground pin and 1×5V pin. 
Only the 12V and ground(s) end up into the video card, PCIe card don't use externally fed 5V. 

HD4850, like majority of modern video cards, that feature an onboard power connector (6pin, eg.) the 12V current they receive from the PCIe slot is only used for minor loads of which video memory power conversion is responsible for the majority. Memory on the HD4850 uses around 35W. 

Basically, if the connector is not plugged the video memory on your cards run on power the ATX24 connector provides. That's less ideal as while travelling through the motherboard the current, that will eventually feed your GFX memory, will surely catch _and also create_ some signal interferences. If you plug it in you provide an additional, lower resistance and less EMI-ridden route for the electricity between PSU and GFX meaning atleast half of the power will flow through the molex rather than the motherboard. 

Summary:
It can't hurt to plug it in.


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## Geofrancis (May 20, 2009)

my gigabyte 965p ds3p had the same connector for the second pci-e slot its just to ease te load on the extra 4 pins of the atx connector that were added for running pci-e. if you were running a card in the second slot without the 6 pin pci-e connector that used close to the 75w that pci-e can supply then i recon you would start running into problems.


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## dark2099 (May 20, 2009)

Maybe look into getting something like this which might not mess with your air flow as much.  If you over clock your cards, the extra power could improve that a bit, plus if you're overclocking the CPU and Ram, then those parts are drawing extra power which the board is only supplied so much by the 4/8pin CPU and 20(+4) ATX.


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## Mussels (May 20, 2009)

it just provides extra power. it can particularly help if your PSU has multiple rails, as you can spread the load better.


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