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HX1000W and GTX295 Sli questions and findings


Kenski

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Just purchased an HX1000 and thought I'd look in here for rail distribution and other info, found everything I need so far... ;):

After browsing through several pages I noticed it stated several times that the 2 Psu rails should not be used on the same Video card (Gpu1 and Gpu2) because of the independant nature of the 2 rails, and I can understand the logic in that for a "single" card, but remembering back when I fitted the waterblock to my GTX295, that it was 2 independant cards, each with it's own Pci express power connector, vrm's etc, the only physical connection between the 2 being the Sli ribbon cable, also noticed that the second card carried the 8 pin connector, while the card that fits into the motherboard slot has the six pin, which makes sense, as it can draw from the mobo too,

In light of this, and the fact that each GTX295 is rated at a max power consumption of 289W, would it then be possible to use different connectors on these cards ?

Having all 4 Pci express connectors going to "12v2" ( 2 fixed, 2 modular ) plus all Molex and sata connections while leaving "only" the motherboard and EPS connector on 12v1 seems a little "unbalanced" considering the 2 x 289W max of the video cards alone, minus of course the 2 x 75w available from the mobo Pci express slot.

having just 1 6 pin power connector from "12v1" would reduce the heavy load on "12v2", or is the HX1000 a little "underspeced" in it's 2 x 40A rating ?

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The loading should be pretty straight forward, you will want to use the fixed PCIE cables for the first card and then the 12v1 modular cables with the next card. Your remaining peripheral devices will draw power from the 12v2. Keep in mind that the maximum power rating for each device it not the amount of power which will be drawn all the time, its just the maximum that it could pull. Normally when you are gaming you will stress the CPU motherboard, video cards, a hard drive and possibly an optical drive. With that said, the HX1000 wattage is fairly under rated in what it can actually provide in real world use.
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So you are saying to run the first Gpu off the fixed cables (12v2), and the second Gpu off the modular cables from 12v1 ?

That would put the second Gpu on the same rail as the motherboard and Cpu correct ?

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So you are saying to run the first Gpu off the fixed cables (12v2), and the second Gpu off the modular cables from 12v1 ?

That would put the second Gpu on the same rail as the motherboard and Cpu correct ?

 

Thats right, here is the diagram:

 

http://www.houseofhelp.com/forums/attachment.php?attachmentid=3676&stc=1&d=1213300906

 

So the 12v1 will power a single video card along with your motherboard and CPU, and the 12v2 will power 2 cards along with your peripherals.

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I only have 2 GTX295 video cards, (maybe the initial post confused the issue) my original question was about the GTX295 being 2 individual boards in 1 housing, each board with it's own PciE plug, vrm's etc, only one of the cards is plugged into the motherboard, the other is only connected to it by the onboard SLi bridge connector, so in effect, with 2 x GTX295's the Psu is really only "seeing" 4 seperate circuit boards,

With this in mind, my main query is, is this hookup possible:

12V1:

24 pin ATX connector,

8 pin EPS 12V

Modular 6pin PciE to 6 pin PciE connector on the primary card of the first GTX295

 

12V2:

Modular 6 pin PciE to 8 pin PciE connector on the second, or "slave" card of the first GTX295

2 x fixed PciE plugs to the 6 pin and 8 pin PciE connectors on the second GTX295,

In theory that would run Cpu, motherboard and 1/2 of the first GTX295 from 12V1, and the other 1/2, plus the second GTX295, + molex and sata from 12V2,

if it was running a lower power Cpu I wouldn't worry too much, but a QX9650 clocked to over 4000Mhz does draw a lot of power,

I realise it's not recommended to run a "normal" Video card with 2 connectors from different rails, but those cards sum the input of the 2 connectors before the cards Vrm's,

Sorry to be a "pest", and maybe I should be asking about the GTX295's "twin circuit boards" in a Gpu forum, but in theory, it "should" work ok, unless I'm missing something.

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Don't worry about each card having dual GPU's, they are still considered a single card when it comes to hooking it up to the PSU. The HX1000 will power your system with no problems at all.
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