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PC Power Supply Discussion Troubleshooting and discussion of computer power supplies

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Old 04-18-2012
sebykos sebykos is offline
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Default Seasonic S12D 750W Load Balancing between the rails

Greetings from Romania,

I discovered johnnyGURU.com in late 2009 when i was planning to buy a new pc and looking after information for choosing a psu. The site and this forum really helped me a lot; here i learnt a lot about power supplies in general, how they work and the parts they ar made of. Though i'm not an engineer, i really liked the electicity chapters at phisics during the high school, so i knew the basics needed to understand the reviews and other articles here, and the fun manner in which they are written made me read with pleasure a lot of them.

I built the computer that i was talking about, in april 2010(it took so long because i was waiting for the nvidia gtx 400 series which launched a lot later than expected). The psu that i've chosen is the Seasonic S12D 750W, not because i needed so much power, simply because here in Romania, sometimes products are overpriced, so this power supply was only the equivalent of 10$ more expensive than a Corsair TX650W at the time.
Well, a month ago i had some very strange problems(freezing, black screens, bsods, artifacts, etc), it was the gtx470 that got broken and the warranty replaced it with a gtx 560TI 448.

This issue reminded me about an old dilema i had when i built the computer, and this is the question i have for you: How is the best way to distribute the load from the computer over the two rails that this psu provides? Or maybe a better question: Does this really matter?

This particular psu model didn't get a review here but his bigger 850W brothers did ,so i got some info about which connectors rely on which rail from this article i found here http://www.hardwaresecrets.com/artic...y-Review/800/6 so:
Quote:
This power supply has two virtual rails (which is unusual for a power supply from this power range), distributed like this:
+12V1 (solid yellow wire): Main motherboard cable, SATA power cables, peripheral power cables, one of the six-pin video card power connectors and one of the six/eight-pin video card power connectors.
+12V2 (yellow with black stripe wire): ATX12V, EPS12V, one of the six-pin video card power connectors and one of the six/eight-pin video card power connectors.
My system's specs are:

CPU: Core i7 930 (sk1366) with stock Intel cooling
Mainboard: Gigabyte x58a-ud3r
Graphics card: Gainward GTX 560TI 448 cores 1280MB
RAM: 3x 2GB Kingston 1600mhz (tripple channel)
HDD: 1TB Samsung 103sj & 2TB WD 2002FAEX
Optical drive: Pioneer DVD-RW
1x120mm and 1x140mm Thermaltake case fans (on molex)

So from the article on Hardware Secrets i leant that one rail feeds the Mainboard connector and the SATA and MOLEX connectors while the other rail is responsible for the ATX12V and EPS12V.

So far so good but how do you suggest is the best way for me to power my graphics card so that the rails will be loaded as evenly as possible, knowing that each rail supplies power to one 6pin and one 8pin pcie connector and my graphics card only requires two 6 pin?

Untill now i used a cable from each rail to power the card. But, can drawing power from two different rails cause any problems to the card? Would it be better to use both pcie connectors from the +12V1 which also provides power to the mainboard and the sata and molex connectors, and leave the other just for the EPS12v?

Thanks a lot and sorry for the very long post and bad english...

P.S. Here we use 220V mains. Also what wold be a decent UPS to buy for this computer? I really don't know how to choose them. Does it have to be at least 750VA to run a 750w psu? I only need it to keep the system running for 10 minutes to save my work and do a proper shutdown. And most of the time the blackouts don't last for more than a few seconds, which is very bad because, the computer turns off and on in a very short time interval.

Last edited by sebykos; 04-18-2012 at 04:29 PM.
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Old 04-18-2012
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It doesn't matter because the M12D / S12D 750w / 850w units are only single-rail not multi-rail.
They don't actually have that second 12v rail, as it's just a large single source that Seasonic arbitrarily divided up.

If you want, you can see the modular PCB in this picture (link) and V1 = the 1st 12v Rail, while V2 indicates the 2nd 12v rail.
Connect your drives & CPU to the 1st 12v rail and your GPU to the 2nd 12v rail; and that would be balanced out for the most part.

In reality, it shouldn't change anything though.
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Old 04-18-2012
sebykos sebykos is offline
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Quote:
Originally Posted by Tator Tot View Post
....
Connect your drives & CPU to the 1st 12v rail and your GPU to the 2nd 12v rail; and that would be balanced out for the most part.

In reality, it shouldn't change anything though.
This can't be done because the drives and CPU are on different rails. The motherboard is on the same rail with the drives.
Also despite i don't have the modular version i can distinguish them because 12v1 ueses yellow wires while 12v2 uess yellow with black stripe wires
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Old 04-18-2012
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Quote:
Or maybe a better question: Does this really matter?
No. Even if you put your entire computer on one rail, you'd be below 40A.
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Old 04-18-2012
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Quote:
Originally Posted by sebykos View Post
This can't be done because the drives and CPU are on different rails. The motherboard is on the same rail with the drives.
Also despite i don't have the modular version i can distinguish them because 12v1 ueses yellow wires while 12v2 uess yellow with black stripe wires
Like Raf & I both said though, it won't matter.
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