building this up for a mate and i got rid of my 2 2900xt's i had in Xfire (i have a 1200W TT) for a 3870x2 but my mate only has a enermax liberty 620W. its not gonna cut it is it? he also has a 6400BE oc'ed to 3.5 and a TT Kandulf 4gig giel value ram and 3HDD 1 dvd drive. Quality brand pls. i get confussed with amps needed with how much watts it puts out.

pls help

620w might be cutting it too close, you are right. A PC Power and Cooling Silencer 750w should do it, or the Thermaltake 850w power supply. Either way I would have to say you should be fine with either power supply. From the calculators I have ran, the maximum draw from the power supply seems to be 700w or less, and thats overestimating his system as much as possible. Also the PC P&C is rated to be able to take 750w constantly and almost 900w peak. Remember the the 700w is with everything at absolute 100% and all possible fans and lights installed un that Kandalf.

Hope this helps, and good luck.

Its a strong PSU but it maybe a little short in a full load situation.

http://www.atomicmpc.com.au/forums [...] c=7&t=9354

Max 2900XT in crossfire can reach 350w+ considering the CPU is overclocked and the possible age of the PSU (will deteriorate over time) i would also suggest going for say the PCP&C as The_Blood_Raven suggests

PCP&C are pretty hard to get a hold of in oz so i think the TT 850W will do it. is that gonna be the best one of should a corsair or enermax be better for the job

Corsair TX-750 750w is getting some good reviews... i too am from AUS so know PCP&C aint easy to come by...

ok cool thanks chook. i'll say either the 750 corsair or the 850 TT. does it matter if it is Xfire certified?

No, it will work as long as the cable has the right 6/8 pin PCIE cable. Though some power supplies might have problems with ATI cards, though I do not think those are PSUs with those cards,

the whole certification thing is overated. As long as the PSU has enough amps on the 12v rail, has enough overall wattage and the power connections you need your good to go.

I pulled 605 watts with a single 2900XT overclocked to 930/1100 with an Opteron 185@3.0Ghz. A 620watt PSU won't cut it. You friend needs 850-1000watts to handle that setup. Dang, that system will draw so much power under load its ridiculous. He needs to stick with Seasonic or PCP&C PSUs.

ok thank you for all of your input i really appreciate it. i will recommand the corsair 750, TT 850 or anything over 850W.

Thanks again ppl