question on 6pin/8pin connectors

[YabbyU]

I'm looking at new PSU's and I'm confused by the "SLI Certified"

I'm thinking this is a great deal.

http://www.newegg.com/Product/...x?Item=N82E16817153039
Thermaltake W0106RU 700watt

But are (2) 6pin connectors enough to run SLI if both cards need (2) 6 pin connectors?

I know my 6800 ultra needed (2) dedicated 4 pin connectors and could not use a "Y" off (1) 4 pin.

And finally what are the (8) pin for. I only see those on 800watt and up.

Thanks

 

[mpilchfamily]

If the vidoe card needs 2x 6pin PCI-e connectors then to run a pair of them in SLI will mean you need 4x 6pin PIC-e connectors. If the PSU doesn't have 4 then chances are it doesn't have enough power to run you system. Check nvidia's web site for a listing of the PSUs that will support your SLI configuration. Since your cards have 2x PCI-e power connectors i take it you have either the 8800 GTX or Ultra. So check the dropdown menue and see what PSUs are certified to power your setup.

http://www.slizone.com/object/slizone_build_psu.html

The 8 pin PCI-e connecotrs can be found on smaller PSUs then 800W units. Corsairs VX 550 and there TX line all have 8 pin connectors. The 8 pin will work on regular 6 pin connections just 2 pins hang off to one side. Ofen the connectors are 6+2 pin connectors so thay can either be a 6 pin or 8 pin. The new PCI-e 2.0 spec adds the 8 pin connector to help power upcoming vidoe cards that have higher power needs. So far no video card needs an 8 pin connector yet.

 

[seriousturtle]

exactly the card that i was looking at. but its the amps that confuse the hell out of me, and i've read hours of forums full of disagreements about how amps and rails work. this card http://www.newegg.com/Product/...x?Item=N82E16817153039

says it has 4 12v rails running at 18amps each. and this evga 8800gts (for example) http://www.evga.com/products/m....asp?pn=256-P2-N768-AR
says it requires 12v @ 22amps.

Requirements
Minimum of a 400 Watt power supply. (Minimum recommended power supply with +12 Volt current rating of 22 Amp Amps.)
Minimum 450 Watt for SLI mode system. (Minimum recommended power supply with +12 Volt current rating of 24 Amp Amps.)


so are these two products compatible or not. and the gtx's are requiring even more amps, like 26-30. can someone explain this who KNOWS what they're talking about? would really appreciate it, since my upgrade is waiting on the psu and vid card. thx a bunch

~the turtle

 

[mpilchfamily]

Link is bad but i found the PSU you are looking at.

http://www.newegg.com/Product/...x?Item=N82E16817153039

Now keep in mind that the requirements mentioned for the video card are for a full system and not just the card. So the amperage rating listed is total amperage from the combined +12v rails. The PSU says it had 4x +12v rails rated at 18A each. But you don't add up the 4 rails to figure the total +12v rail's amperage. For that you look at the label and find where it mentions the total wattage being supplied to the +12v rails for which that PSU doesn't list. So its hard to say exactly how many amps are available to the +12v rails. A good estimate would be about 30A. So you should be fine with that unit.

You may find this a good resource of information about PSUs.

http://www.xcpus.com/forums/ca...ide-psu-101-102-a.html

 

[YabbyU]

Thanks for the help Mpilch....

Turtle, I think the Psu we are considering is plentyto power the GTS as it has 56amps total. My main concern was it only has (2) 6 pin PCI conectors. This is fine for the GTS, even in sli, but if you were to upgrade to a GTX/Ultra or some future card that takes (2) connectors each, you couldn't run in SLI..... unless I'm missing something.

I decided to go with something that has at least (4) 6pin and I'll probably go (2) 6pin and (2) 8 pin to help "Futureproof"

Still looking for one though.....

 

[seriousturtle]

thx for your help mpilch. in lots of other forums, ppl stressed having the right amount of amperage on each rail as opposed to watts. so im a little confused about "adding" up the rail's amperage, combining them, or keeping them separate. right now i'm gonna look at the link you posted. thx again.

~the turtle

 

[Deleted member 4644]

Must power supplies cannot "add" their rails. For example, I have an HX620 which has three 18am rails, but the total power supply on the three rails is actually only 50A.

18x3 = 54. So I lose at least 4 A on the "combined" rails.

 

[mpilchfamily]

You don't loose any power. First of all even though the label on that Corsair says it has 3 rails its only a single rail. If it was a 3 rail PSU those 18A are the max amount of current that rail can handle not what it actually gets. The PSU only has a max of 50A it can offer to the rails.

Now depending on how the connectors are divided among the rails, if the HX620 was a multiple rail PSU, will determine the amount of possible amperage that can be drawn threw that rail. Where you have amperage lost is in actual multiple railed PSUs. Lets say the Corsair had actuall 3 seperate rails rated at 18A max and can offer a max of 50A on the combined +12v rails. Well 1 rail would be dedicated to the CPU/Motherboard, another would be for the PCI-e connectors and everything else would be on the last rail. So your max possible amperage on each rail will be as follows.

+12V1-> 9A-14A
+12V2-> 12.5A (each PCI-e connector is speced to supply a max of 75W or 6.25A)
+12V3-> 18A

So in total the most you could pull from the PSU would be about 44.5A. Even if you where to OC the CPU to take the full 18A the +12V1 rail is able to safely have pass threw it you would be 48.5A. So you are loosing about 1.5A to 5.5A. On a single railed PSU you don't have that power lost because all the connectors are tied to a sigle rail and have the full 50A available to them. I think i have it all explained better in the link i offered above.