Gtx 280 + PSU

[jonnydexter]

Hi all

i just need to clarify a little information about a psu suitable for running a gtx 280 after frying a couple recently. basically i have two pc's which i want to add gtx280's to. I know these cards require a high ampage to run efficiently, but as each card take power both from the mainboard and the 6 / 8 pin power connectors i wanted to check something.

i am assuiming both the 6 and 8 pin need to be connected to get these beasts to run properly but what requirements are needed on the 12v rails to get a steady - reliable feed. if multiple 12v rails are used i am guessing that each group of molex/sata connectors are on a 12v rail, so as long as the cards connectors are placed on a molex for a different rail what is the minimum ampage that rail needs to put out ?

do i need a minimum two rails putting out 25 amps each ( considering that drives need some power as well) or must each rail support a high ampage of 40w+ ?

i hope this makes sense to someone, and they can answer my question.

I have 2 pc's to drop 280's into and with the psu's coming in at around £60.00 a piece(xfx 550w pro edition - if i m lucky) - it could get very expensive very quickly if i make the wrong decision.

thanks in advance for any help

 

[clutchc]

You're over-thinking this. Use this calc to estimate the size PSU for the total system: http://www.thermaltake.outervision.com/

Any good quality PSU that is big enough to run a card that requires 2 PCIe connections will have at least 2 PCIe power cables. You shouldn't have to go adapting Molex connectors to PCIe connectors. The GTX 280 requires a max of 230W with 19.2A available on the +12V rail... at max. PSUs with more than one rail will have multiple PCIe power cables wired to separate rails. (not that that matters all that much) Any good quality 550W or larger PSU should be sufficient depending on how heavy the rest of the system is. To be on the safe side, personally I'd go no less than 600W.