single 12v rail on 780i ??

dgb0002 · February 10th, 2009, 11:39 AM

I am looking to upgrade my power supply and was wondering about the 12v rails. Currently I have an EVGA 780i SLI mobo and it has outlets for two 12v rails, but I was wondering - can I get a power supply that has a single 12v rail, or does it need to have 2? Also, could I get one with MORE than 2 rails?

railfrog · February 10th, 2009, 12:51 PM

Quote:

Originally Posted by dgb0002

I am looking to upgrade my power supply and was wondering about the 12v rails. Currently I have an EVGA 780i SLI mobo and it has outlets for two 12v rails, but I was wondering - can I get a power supply that has a single 12v rail, or does it need to have 2? Also, could I get one with MORE than 2 rails?

Not too sure what you mean by two outlets on the MOBO.

Yes you can get PSU's with single, dual, triple and even quad rails.

ShyguyXPC · February 10th, 2009, 03:52 PM

even more than 4 rails, I've seen some with 5 or 6 rails.

but agreed on the two outlets part, have no clue what their talking about there... unless maybe their referring to the normal 24 pin connection and the extra 4 or 8 pin connection?

in which case, those have no real bearing on the number of 12V Rails on the PSU.

dgb0002 · February 10th, 2009, 11:58 PM

Sorry for the confusion. What I meant was the 8-pin CPU power. Is that not what is meant by 12v rail?

ShyguyXPC · February 11th, 2009, 12:35 AM

nope, 12V Rail is one of three voltage rails in the PSU that provides power to various system components in the system...

the 8 pin, or in many cases these days 4+4 pin is an additional power connection on the motherboard, just as years ago with the Pentium 4 they introduced the "P4" connector, now they have an additional 4 pins added to it for even more suppplementary power for the CPU & whatever else.

found a good read on Power Supply Rails: Power supply rail - Wikipedia, the free encyclopedia

but generally when their talking about the +12V Rails, its in reference to the video cards. there's still an ongoing debate whether a single rail is best or multiple rails...

what power supply do you currently have?

also what are your system specs?

primarily CPU, amount of RAM, video card, etc etc? (we already know the Mobo, but whats all in it)

we might be able to help suggest some PSU's that would be good replacements for whatever you have now...

dgb0002 · February 11th, 2009, 01:43 PM

Q9550(E0) @ 3.4GHz
2 x 2GB OCZ Reaper @ 800MHz (1:1) 5-5-5-15
EVGA 9800GTX @ 800/2000/1250
2 x 640GB WD Caviar (RAID 0)
EVGA 780i SLI (FSB @ 1600MHz)
OCZ GameXStream 600w
Antec 1200 Full Tower

I like to push my system, so I will need a power supply that can accommodate overclocking well. And the only reason I'm getting a new power supply is because I am going to get a GTX 295 soon. I was thinking of getting an 800w.

Atomic Rooster · February 11th, 2009, 01:50 PM

The GTX 295 requires a minimum power supply of 680W with a +12 Volt current rating of 46A. So really, any quality 700W and up power supply will do well in your system.

ShyguyXPC · February 11th, 2009, 02:15 PM

a GameXStream 700W will do fine, but the only down side is the lack of any 8 pin connectors, in which case you'd need an adapter for, which is often not recommended to do, for extended periods or on high end cards for whatever reasons.

the Corsair 750W model I just bought (should be here tomorrow hopefully) to replace my GameXStream 700W for Just That reason, would be a good one, its 750W, good quality, has 4x 6+2 pin, plenty of amps (Single 60A rating on 12V), picked it up on newegg for about $120 last week, looks like it went up $10 though.

would be a good start: Newegg.com - CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Power Supplies

for a bit more, the 850W model can be had:

Newegg.com - CORSAIR CMPSU-850TX 850W ATX12V 2.2 / EPS12V 2.91 SLI Ready CrossFire Ready Active PFC Power Supply - Power Supplies

Single 80A on 12V with that one.

Atomic Rooster · February 11th, 2009, 02:25 PM

This would work well too: OCZ ModXStream Pro 700W - $104.99 ($84.99 after $20.00 Mail-In Rebate) with Free Shipping.

It has a 6+2 pin PCIe connector and 50A on it's dual 12V rails.

ShyguyXPC · February 11th, 2009, 03:49 PM

keep in mind its a dual rail, so you won't necessarily get the full power, it shows 552W for both, doing some basic math, even though its not entirely accurate, that comes out to 46A on the nose... so just barely enough for the GTX295 with little room to spare.

but even with that said, its not bad for a start and the price.

but aside from the connectors (1x 6 pin & 1x 6+2 pin) its not much different from the PSU he has already, and as far as the 12V rail goes, its a step back really.

slightly better choice would be this one: Newegg.com - OCZ StealthXStream OCZ700SXS 700W ATX12V / EPS12V SLI Ready CrossFire Ready Active PFC Power Supply - Power Supplies

same connectors & number of them, but non modular, & better 12V amp rating, not to mention cheaper & assuming the rebate goes through MUCH cheaper.