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Dazed & Confused in PSU land with X-Fire 4870s

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February 13, 2009 11:49:03 AM

Catchy title huh... so my upcoming build will be my first. Been researching for ages (about 2 months) before i bought my parts. Though i bought only one 4870 1gb i plan on added another in maybe 6months-year. For this reason i made sure everything was x-fire certified including my psu which is an antec earthwatss 650w (http://www.newegg.com/Product/Product.aspx?Item=N82E168...). The 4870 1gb needs 2x6 pin to power. my psu comes with 2 but wont i need 4 for crossfire. Im new to this so i dont understand modluar and maybe i can get adapters to make 4x6 pin plugs. please help explain and if this psu is not good enough can you reccomend ones that would be good for a 2x4870 1gb xfire setup. thanks
a b ) Power supply
February 13, 2009 12:13:13 PM

The Antec Earthwatts 650w PSU is a high quality unit and will have no issues powering CF 4870s.
All you will need is a pair of MOLEX to PCIe 6pin Connectors.
February 13, 2009 12:36:07 PM

thanks for the quick reply. ive looked at this before but i dont quite understand how they work, does my psu have these extra power cords to convert?
February 13, 2009 12:40:39 PM

im sorry disreguard that basically i checked my psu's stats and it says i have 6 molex connectors. so what you are saying is 2 of these adapters will use 4 of my molex connectors to power another 4870 1gb. am i correct?
a c 139 ) Power supply
February 13, 2009 2:48:00 PM

Some video cards come with the molex to PCI-e power cable in the accessory pack.
For example looking at Sapphire and PowerColor 4870s at the same price the Sapphire has the power cables in the accessory pack and the PowerColor doesnt.

February 13, 2009 2:55:43 PM

ahhh thanks dude that was the perfect answer. yes i bought the sapphire 4870 1gb so those 2 cables on the left are the molex adapters. wow i feel so much better now that my psu is aok. i found it strange that theres only a few 4x6pin psu out there when so many ppl crossfire and sli.
February 13, 2009 5:47:41 PM

hey i just want to make sure you guys think the ea650 will be able to stand up to 2 4870's 1gb right? there is no definitive source to give an answer and i get mixed responses
a c 139 ) Power supply
February 13, 2009 8:17:41 PM

Look on the Sapphire 4870 web page.
Look toward the bottom of the page where it says System Requirements.
It says what they recommend for 2x 4870 in CrossfireX dual mode.
February 14, 2009 9:29:45 AM

500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)”

That is what they say... ea650 has 650watts 3 12v rails 22a,22a,25a. the pci express connectors are on the 25a rail and im assuming the next 4870 will have to be power by adapters on a 22a rail. like i mentioned before im in the beginning of my psu knowledge. how does it look? am i cutting it a little too close?
a b ) Power supply
February 14, 2009 1:11:58 PM

http://archive.atomicmpc.com.au/forums.asp?s=2&c=7&t=93...
4870 CF max 255W
for quad cpu with high oc 150W, 100W for oced dual, maybe 50W for stock dualcore
each drive 10W
mobo 20-30W
each fan 1-5W
all these are max loads for 12V lines, your psu has 540W combined on the 12V lines. don't go too much over 450W or you'll be pushing the psu pretty hard. Antec makes good quality units but pushing it might shorten its lifespan somewhat. Also the efficiency usually decreases with very high loads
February 14, 2009 1:30:37 PM

great info dude so lets list it out worst case for my setup...
4870 cf 255w
e8400@3.8ghz 100w
dvd drive 10w
640gb wd hard drive 10w
ep45 ud3p 30w
rc 690 3 fans 15w

all equal to 420w so this is worst case max loads all should be good correct? i also got the 79.99-35 combo deal so i really dont want to spend alot more nd i wont be xfiring for atleast 6 months so im eventually gonna upgrade but for now i should be ok then if what your saying is accurate and it seems right on. thanks alot
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