12v Rails?

Is it better to have a single or can you run multiple? I've heard different stories from alot of people. I plan on crossfiring maybe 2 4890's. I'm looking for some more input on this. Thanks!!
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  1. Are you crossfiring for the fun of it or do you have a 30" monitor? A single 4890 is plenty for up to 1920x1080. As long as you buy a good name brand psu with the right amount of pci-e connectors for your card and support for crossfire or sli for the cards you want, you should be fine. Read up on it, its good to know for yourself.
  2. While the debate raged on some interesting technical information surfaced. There are very few power supplies for personal pc's with true +12 volt mutiple rails. Turns out most of them are one large +12 volt rail divided into "virtual" rails. It appears to be an advertising gimmick more than anything else.

    Modern high quality power supplies do a very good job of distributing power. It doesn't seem to matter whether there is one large rail, virtual rails, or mutiple rails. Buy a good one and be happy!
  3. schwag91 - Are you still here?

    I was just over at Xbitlabs reading a technical review of 7 Antec power supplies. Here is a direct quote about +12 volt rails that might interest you:

    "The Antec website claims that two +12V lines (one of which is connected only to the 4-pin ATX12V connector) ensure stable power for the CPU that does not depend on the consumption of the other components. As I have repeatedly noted in my reviews, this is untrue. There is but one 12V power rail inside the PSU. It is split into two lines at the output in order to make the PSU safer for the user. Thus, there is no talking about the two lines being independent. Except for the tiny difference due to the voltage drop on the wires and connectors, the voltages of the 12V1 and 12V2 lines are almost identical. If one sags, the other sags, too."

    You can read the entire review at:

    http://www.xbitlabs.com/articles/coolers/display/antec-psu-roundup.html
  4. Wait and get the 4890 x2. It was just today approved for sale. So expect it in the near future. It has been benched in its prototype form and is supposedly better than the GTX 295. Impressive. Just wait to get the better performance form the 4890 x2 instead of 2 4890's in Crossfire. And in the future you can Quadfire those bad boys and get unreal performance.
  5. JohnnyLucky said:
    schwag91 - Are you still here?

    I was just over at Xbitlabs reading a technical review of 7 Antec power supplies. Here is a direct quote about +12 volt rails that might interest you:

    "The Antec website claims that two +12V lines (one of which is connected only to the 4-pin ATX12V connector) ensure stable power for the CPU that does not depend on the consumption of the other components. As I have repeatedly noted in my reviews, this is untrue. There is but one 12V power rail inside the PSU. It is split into two lines at the output in order to make the PSU safer for the user. Thus, there is no talking about the two lines being independent. Except for the tiny difference due to the voltage drop on the wires and connectors, the voltages of the 12V1 and 12V2 lines are almost identical. If one sags, the other sags, too."

    You can read the entire review at:

    http://www.xbitlabs.com/articles/coolers/display/antec-psu-roundup.html


    Thanks. I'll check it out!
  6. schwag91- Check out the link Silverion77 posted. It's definitely worth reading.
  7. Johnny, yes, indeed. I have two Antec's - a 650 watt TP3 and a 550 watt TP3 (both bought on sale). They each allegedly have three 12 volt rails. On both of them, if I ohm from any 12 volt line to any other 12 volt line on any connector, I read a direct short.

    Not a problem. I do not need to worry about load balancing.
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