TechSpot

Power Supply for Crossfire

By LipsOfVenom
Jul 14, 2006
  1. I just received 2 X1900XTX's but I only have a 400W PS. What brands are recommended in the $40 - $100 range? Also I read something about needing 30 amps on the 12 V rail. So is that the only rail I need to keep my eye on? Basically I just want something to run these 2 behemoths. Thanks for your advice.
     
  2. KingCody

    KingCody TS Evangelist Posts: 992   +8

    1. a good 400w power supply should already have 30 amps on the 12v rail

    2. the ATI specs state 30A for single card, and 38A for crossfire.

    3. yes, generally the 12v rail is the only one you need to worry about (the other rails will pretty much have more than enough power if the 12v rail is high)

    as far as good brands go. I personally would recommend Antec. other reputible brands include Enermax, fortron, PCP&C, and seasonic. The reason I like antec so much (aside from the high quality and reliable protection circuits) is because they rate their PSUs actual power output accurately.

    if you are willing to spend $100 and want an awesome PSU, then check out this beast!, it's got three (yes 3!) 12V rails at 17A each for a total of 51A on the 12V rails. and with modular cables and a single 80mm fan @ only 18dB... what doesn't this PSU have or do??? Antec rates this PSU at 500w, other PSUs with as much power as the NeoHE 500 would be rated much higher (i.e. 600w or more)

    hope this helps :)
     
  3. Mugsy

    Mugsy TS Guru Posts: 361   +9

    Not gonna do it.

    400w? Ouch! That's not gonna do it.

    I'm afraid that you are going to have consider spending more than $100 (as for $40... no freakin' way!) :)

    The MINIMUM I'd recommend nowadays with the new cpu's, tons of fans, and PCI-x video cards with monster coolers is 550w. Even 480w is a cutting it close nowadays.

    I just bought a Thermaltake ToughPower 550watt power supply... the *smallest* they make now. It cost me $119 new. Their top-of-the-line psu is 750watts for $180-$200. All ToughPower psu's are Crossfire ready. The higher end models have removable cables to reduce clutter in your PC to improve airflow.

    With todays' machines, 400w just isn't going to cut it anymore. Where 550w used to be huge, now it is the minimum.
     
  4. KingCody

    KingCody TS Evangelist Posts: 992   +8

    even with today's machines. most PCs will still need no more than 350w if it's a quality brand PSU.

    you overemphesize wattage because you buy from brands like thermaltake which state high wattage, but they're actually low power units. your 550w toughpower only has 29A on the 12v rail. my 380w antec has 32A, what does that tell you???

    if you have a high end video card, a good 450w will cover it, dual cards move up to 550w.

    $100 will indeed be enough for a quality PSU that will have more than enough power. the Antec NeoHE 500 has 51A. which means that it's almost twice as powerful but actually rated for less wattage.

    i don't think thermaltake makes bad PSUs, but they are very underpowered for the wattage they state.
     
  5. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    I completely agree with KingCody.
    My cousin thinks he has a better PSU than me. He has an "A-power" (TERRIBLE BRAND) 450 watts PSU, but only with 15A on the 12V rail.
    I have (currently) a "small and underpowered" (for him) 300W PSU, but with 32A on the 12V rail.
     
  6. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,431   +28

    I use an OCZ GameXstream PSU. It's 700W and runs the cards and everything else comfortably. Plus it's certified for Crossfire support by ATi. it's around $100-$140 though. The model number is OCZGXS700.I'm giving u the model number coz there's another 700W PSU that's certified only for SLI. BTW there's a 600W Crossfire-ready PSU also available but I'd recommend the 700W one since I use the same configuration of cards and I've had no problems so far.
     
  7. mailpup

    mailpup TS Special Forces Posts: 6,979   +362

    I just bought a 650W Mushkin (known mostly for their RAM). This is new item for them but it sports four +12V rails with 20amps each. One interesting feature is it automatically combines rails if there is high enough power demand. It just arrived yesterday so I have no experience with it yet. Very heavy though.
     
  8. Mugsy

    Mugsy TS Guru Posts: 361   +9

    Better than you think.

    Find me a "quality" 350w psu that can support two Crossfire vidcards. No such animal.

    That you don't know the difference between volts & amps for one. <jk> :)

    My ToughPower has 38amps on the 12v rail, not 29. Compared to your 32... what does that tell you? :)

    He said he wants to run dual x1900's.

    Check its stats here:

    http://www.thermaltake.com/purepower/w0096-97/w0096-97.htm
     
  9. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,431   +28

    Yeah mailpup that's the case with the OCZ Supply too. A review of the available PSUs for Crossfire shows the OCZ to be the best in performance, stability and durability. Plus it's highly efficient and lighter and cheaper than other PSUs like the Mushkin(also reviewed here)
    http://www.legitreviews.com/article/348/14/
     
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