Power supply question 3v vs 4v VGA connections

Hello all,

I am still a n00b with power supplies , so here is my question:

I have a thermaltake thoughpower 1200w cable management, and there are 6 connectors from the power supply for VGA , 3 are 4V and the other 3 are 3V and I was wondering where should I connect my vga power cables ? and what is the difference with 3V and 4V ?

I mean , if I buy a 5970 HD where should I connect it ? How can I setup a SLI/Cross fire ?

Thank you

PS: link to a picture of the power supply connectors exactly as the one I have http://img693.imageshack.us/img693/9868/puc1200v04.jpg

EDIT: Also and good to know , is this power supply good for a 5970 HD ?

the V3 and V4 are likely talking about the individual 12V rails. basically, you want one cable from V3, and one from V4. the HD 5970 uses one eight pin PCI-e power cable, and one six pin PCI-e power cable, so be sure to connect both, with each cable hooked up to a different rail for better distribution.

and yes, that PSU is good enough for a 5970. it's actually way overkill, in fact.

Hi Moriz , thank you for the answer , I get the point , but if you look to the picture is quite tricky I think..

There are 2 4V with 8 pins(blue in the picture) and 1 4V (blue) with 6 pins . 2 3V with 6 Pins(red) and 1 3V with 8 pins (red).

Is the sticker wrong ?

not necessarily. it's possible that each rail has different power outputs, hence why one rail gets two 8 pin connectors, while the other gets two 6 pin connectors.

if in doubt, just pick the top left 8 pin, and bottom right 6 pin.

of course, if there's an instruction manual, go with whatever that says.

I think you are getting things confused. The connectors are not 3Volt and 4Volt (and 1Volt), they are simply V1, V3 and V4. They could just as easily have marked them as R(ail)1, R3, and R4.

Do as Moriz says.

Thanks Quaker , and yeah , I am getting confuse here, maybe lack of coffee ? lol

I was reading the manual and there is a warning: please be noticed that when trying to connect more than one connector to a graphic card, it is strongly recommended to choose the connectors from exactly the same +12V rail

How do I know witch ones are from the same +12v rail ?

Also I have 3 red cables that says +12v v3 rail and 3 blue cables that says +12v v4 rail.

You've just answered your own question ^_^

All the +12v v3 cables come from the same 12v rail, all the +12v v4 cables come from another 12v rail.

In a nutshell: The rails are numbered v1, v2, v3 etc., so you need to take a +12v cable from two different v-numbers.

(edit) ...although, wait a minute. That instruction to use multiple connections from the SAME 12v rail would be the total opposite to what I've always been told. I'm stepping out of this mess right now - moriz and Quaker are the smartasses round these parts )

hmm, that's strange. you'd think by having the graphic card spread across two separate rails would give you better distribution of power, instead of putting a lot of stress on one rail.

go with whatever the manual says i guess.

Does that means I need to connect the video card to two v4 +12V rail. Or it can be two v3 +12V rail. And like moriz said , connecting one from v3 and one from v4, what happends then ?

So according to the manual if I want to setup a tri SLI/Crossfire I am **** , because if I follow what the manual says , to connect exactly the same rail . Then I don't understand why this product is said to support up to Quad SLI , if I cannot even connect a tri SLI.....

EDIT: I think they mean quad sli with a 9800gx2

the recommendation is probably for those who run multiple graphic cards. in this case, having a rail per card is a good idea. if you are only going to run one 5970, i don't think it matters which rail(s) you connect it to.

you won't be able to run quad gpus unless they only take 1 PCI connector each (which is becoming rare in higher end video cards) I would run one video card off the V3 rail and the second card off the V4 rail - just like the manual says. Seriously though that PSU is more than sufficient for any combination of video cards you can plug into it... no worries there.

Quad SLI = 2x 9800gx2 like I had long time ago , but is not that good anyway...

Well no more doubts now , thank you all for your help

You need to connect the video card to either two V4 connectors or two V3 connectors (assuming that V3 and V4 are separate rails.)
Do not connect one connector to each rail.
The two rails, while both being nominally +12v, would vary a bit from exactly +12v. One could be +12.4 and the other +12.3 - the small voltage difference between them could lead to all sorts of strange cross-current and overload conditions as one rail tries to regulate the other. (The 2 power connectors on the card are not necessarily isolated from each other within the card.)

Each card should be connected to only one rail. For SLI, one card could be connected to V3 and the other to V4. For Tr-SLI, you would have to connect 2 of the cards to the same rail, but that's shouldn't a problem, especially with a supply that powerful.
Just make sure that the 2 connectors on each card, come from the same rail.