PSU w/ Crossfire 6950

AnToN_CheZ

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Sep 18, 2011
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Hey guys, first post! Go easy...... :)

Coming back to the PC market after around 6 years on console, I have a system built for the upcoming games toward the end of the year. I have a single 6950, and am considering getting another one to crossfire.

My question: I have a Coolmaster 650W PSU, and from what I can tell, it only has 2 6 pin connectors that the 6950 requires for power. I am not running very much in my build (1 blu ray, 1 HDD, AMD 1090T OC @ 3700MHz w/ Coolermaster CPU cooler, 2x4G 1600 RAM). Will I need a new PSU to run the second card, or can I use the adapters that come with the card to convert the spare regular power connection to the 6 pin PCIe? The system is only a month old, and just want to know if its worth doing now, or if I need a new PSU, I might leave it for early next year, and grab some other things in the process.

Any help would be greatly appreciated. BTW, I used one of those power consumption estimate sites to input all my data WITH a second card, and it gave me an estimate of 550W power usage.

My exact model of PSU is Coolermaster GX Power 650W PSU (AUD $95) if this helps.

Thanks in advance!
 

AnToN_CheZ

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so would I be best off to wait until next year, get a new power supply once I have at least had some use out of this one, and get one that is certified to run 2 x HD 6950's?

Or am I still able to run 2 on my current power supply? Will it cause problems if it is not on the certified list? I am currently running my card at 1.175v, 900Mhz clock and 1450Mhz memory, no problems in games and stress testing
 

AnToN_CheZ

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yes that is my PSU. With that one though, there are only 2 x 6 pin PCIe connectors, and I will need 4 to run both cards.

I have the 4 pin to 6 pin PCIe converters (x2) that came with my card, and will obviously come with the new card when I get it. Will there be any problems using these to power the second card? They will be used on spare 4 pin sockets, not being split or paired with anything else.

I apologize if my terminology is incorrect, I have not been part of the PC scene for some time. Thanks for understanding, and also for any help.

If I am able to use the connectors, I will grab a card today or some time this week for sure! They come in the box so I gather they can't be harmful, maybe just not optimal?
 

pepe2907

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You will be very close to the limit of this PSU. I don't know exactly /and probably nobody can say exactly/ how much power adds overclocking of this processor, so - it's hard to tell. You may experience problems when you put your system under load. And even if the PSU bears the punishment you may drastically shorten it's life
 

AnToN_CheZ

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i punched in all my system details in to the calculator on the PSU link posted above, and the total usage comes to 555W, that includes the second card, but not overclocking.

If overclocking even uses say 15% extra on top of the estimated total , that still brings me in just under the 650W my PSU provides.

I guess if I kill the PSU, it wont really matter, because I will need to upgrade it regardless. So maybe just upgrade to a monster one when it does eventually die running my new setup. May be time for a system overhaul by then anyway. I don't see myself having anything in this build except for the case and blu ray in 2 years time.

If I get that long out of it, I will be happy. Sorry to hammer on this subject, but the 4 pin to 6 pin adapters, nobody has touched on those yet. I gather I am able to use them provided I have the available 4 pin ports (I will need 4, going to check now....)

Many thanks
 

beenthere

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FYI- The numbers don't support your conclusion so it's unclear how you reached it?????? :??:
 

AnToN_CheZ

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thanks for all the help guys. What started out as a semi budget build, has turned into me wanting to make it a bit of a monster. It gets addictive when you start to see the results of new tech, I have been used to 5 year old console tech for a long time.

Thanks everyone for your guidance
 

pepe2907

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Actually they do. Your own too. I estimated your system power requirements to about 560-580W /a rough estimate/. Add to that the extra power for overclocking - and as you mentioned it yourself, you are close to the limit of your PSU.
For your information - it's simple. Be welcome to ask again.