Power Supply Needs, help?

Discussion in 'General Hardware' started by Trigunflame, Jun 12, 2007.

  1. Trigunflame

    Trigunflame Member

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    GPU:
    EVGA GTX 480 SC+ 850/2000
    Ive been browsing/searching around the forums and misc other places and can't seem to find a definitive answer to a question of mine concerning the amperage needed on whichever power supply I chose.

    For example I am building a new system and am probably going to buy an AMD 64 x2 6000+ and throw in either a X1950XT or 8800GTS depending on the money I have to spend along with the various other parts I need to buy.

    Some of my following questions are:

    1. How much total wattage should be sufficient to run without worrying if Im starving the components for power.

    2. How much amperage do I Need Per Rail (Is it 12v Rails); or is it across multiple rails that matter?.. ie say someone suggested that I need atleast 25amps on 12v rail, and my power supply comes with 2 rails both rated @18amp per rail giving me @36 across both.. would that mean it's sufficient? Or does it mean I need atleast 25 Per Rail.

    Peoples comments on various sites ie. newegg confuse me on this matter; thanks for helping.
     
  2. linderman

    linderman Member Guru

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    you are going to receive a wide range of answers to this question, mainly becasue your question is not a pass or fail kind of thing


    buy this I mean there is a concenus of people who belive and are very commited to believing that 500- 550 watts will power anything / this is based on the single aspect that most high end machiens wont consume more than 400 watts from a wall socket at any given time. and this statement is accurate and I wont agrue in most case, although far more than that has been pulled from the wall with high end quads

    the rub comes in here; how long can a 500 watt PSU deliver that 400 watt load ?????? most electrical devices dont like to sustain a load or more than 60% of their rated "real" capability for extended periods (2 years and more)

    that said, (i am taking a shortcut now) the antec 650 watt PSU will deliver the power you need for ONE 8800GTS for more than three years; I base this on the fact slizone.com has certified the antec trio 650 for a system with 7950 GT's in SLI which is the same load as one 8800GTS, SLIzone.com requirements are a service life of the manufacturers warranty period (antec 650 = 5 years)


    There are many others of course that will deliver this too, the Corsair 620 does, the OCZ 700 watt the Silverstone OP750 Thermaltake toughpower 750 does this also

    now; you may get posters here that will say a Corsair 520 will do that ????? To that I would ask, who will "certify" that claim ????? provide links please?

    I have recently seen a review by the hardware canunks who are affiliated with jonny Guru, they stated "only" use a minimum or high quality 700 watt PSU to run even 8800gts Sli >>>>> now if you dont want to run sli (dual video cards) and think for sure you will NEVER want to run SLI ...... then you could deduct 125 watts from the "minimum" 700 watt PSU is needed
    reccomendation; thus leaving you with a 575 watt PSU >>>>> so therefore you are looking for a 600 watt PSU of very high quality ????? or a 650 watt PSU of alittle bit lesser quality like the antec 650 for about $99.00 >>>>> $75.00 if you are willing to get a refurbished unit with only 15 day warranty ????


    ok dudes


    I got my helmet tightened, let er fly
     
  3. linderman

    linderman Member Guru

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    the biggest and most effective way to determine if the PSU you are about to choose is any good ????? what temp is it rated to run at ??????


    the Corsair, Antec trios, Seasonic, PC Power & Cooling are rated for 50C temps

    The OCZ is rated for 40C


    I will check on the thermaltake toughpowers ????? and silverstone models

    if they dont state 40C or above, then they are playing games with the ratings of their units

    by that I mean

    I could sell a car that gets 60 miles per gallon (but it only gets this milage when going downhill on a 20 degree incline

    am I lying about the rating ???????? you decide
     
  4. Trigunflame

    Trigunflame Member

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    Thanks for that reply btw;

    To answer your response, I'm willing to pay a fair price for said PSU's; going the cheap route is not what I'm looking for but at the same time i'm not like for 1k watt PSUs that I will never need, lol.

    Basically these are the components Im looking to run ATM;

    AMD X2 6000
    X1950XT OR 8800GTS (Not Doing SLI) 1 Card
    Video Cards
    1 PCI
    1-2 Hardrives
    2 CD-RW/DVD
    2 Case Fans

    Im willing to spend < $200 on the PSU, the lower the better; but Not sacrificing quality.
     

  5. Infested Nexus

    Infested Nexus Ancient Guru

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  6. linderman

    linderman Member Guru

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    GPU:
    Ati 1600 Pro
    first choice >>>>> seasonic 700watt


    second choice Thermaltake 750 toughpower


    third choice >>>>> corsair HX 620


    Fourth choice >>>> antec 650 watt (the $$$$ vs performance is here)

    fifth >>>>> OCZ 700 watt
     
  7. Trigunflame

    Trigunflame Member

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    Again thanks for the replies, but what I still fail to understand is are these references implying that I need that many amps on a Single Rail, or That Many Amps Combining all of the 12v rails.

    For example this PSU here:

    http://www.newegg.com/Product/Product.aspx?Item=N82E16817153035

    Has 4 12v rails @18amp per rail. And say my Video Card needs atleast 25amps; would this PSU be sufficient?
     
    Last edited: Jun 13, 2007
  8. Trigunflame

    Trigunflame Member

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    To generalize this even further. Do multiple rails share amperage? That is the real question; if I need 25amps for a video card and say the power supply has 2 12v rails @18amps, which would bring the combined to 36amps.

    Would that be sufficient assuming I'm still using only 1 of the rails for the video card?
     
  9. linderman

    linderman Member Guru

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    Hello Tri-Gun


    if you want a really good "multi- rail class" there is a sticky about this topic at the top of the hardware forum

    but to summarize in a crude way, the answer is "mostly" yes

    you add the rails together to get the capability of any given unit

    but if you want the most accurate evaluation / then you must find the maximum combined wattage of the 12volt rails then devide that number by 12 and you will get the real combined 12volt amps for the unit, which by the way is a tad short of just adding 4 rails x 18 amps = kind of math


    you have to make two choices; power supplies are the biggest dark secret to unravel of all computer parts; bar none !!

    you have to decide; do I want to enroll in a PSU class or do I want to take the shortcut and follow the advice of experienced computer enthusiasts. IMHO; not everyone needs to enroll in such an overwhelming class.

    instead ask questions about particurlar PSU makes and models, ask the question

    what is the qaulity of XYZ 650 watt

    you should be looking for answers like "yeah, thats a quality unit but you dont need to spend that much" if thats the only negative comment, you are in the right isle!!


    watts can be achieved like miles per gallon of gas; there are hordes of power supplies that are rated by the MFG for 580 watts but yet they cant put our more than 366 watts !!

    this is eliminated by looking for the label which states the rating can be achieved at 50C !! end of strory

    the bull**** units dont list such temps, end of story!
     
  10. Gordon676

    Gordon676 New Member

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    GPU:
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    go for something with at least 25amps or more on a single 12v rail, with at least dual 12v rails( : 12v rails do share amperage.
     
    Last edited: Jun 13, 2007

  11. Makalu

    Makalu Ancient Guru

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    The amperage values listed for the individual 12V rails don't have anything to do with what the unit will output. Those are the levels at which the unit will trigger the over-current protection circuitry and shut down. So, for instance, say you have a unit with two rails each with a current limit of 18 amps and a combined continuous rating of 30 amps. Each individual rail can ouput up to 18 amps of current but not both of them at the same time. If one rail is loaded with an 18 amp draw then that leaves a maximum of 12 amps available to the other rail. If the power distribution is perfectly balanced between the rails then both rails can output 15 amps before the unit will shut down (the 30 amps combined output is also current limited protected and will cause the unit to latch off if exceeded).

    In a dual rail unit the maximum combined rating is usually just a bit less than the number you would get by adding together the current limits for the two rails together. But in units with 3,4,5 or 6 12v rails the number is significantly less. For instance the TT unit you linked to at newegg with 4 rails, each with a current limit of 18 amps, has a combined output rating of 56 amps...multiplying the individual rails gives a number at 72 amps...so that's significantly more.


    The combined rating is like a reservoir from which several streams flow (the rails) but the reservoir can't fill all the streams up to their banks all at once before it goes dry.

    I estimate the peak 12v amperage for the individual components of your system to be roughly as follows:

    AMD X2 6000 + motherboard - 12 amps
    X1950XT - 10 amps
    OR 8800GTS - 9 amps
    1 PCI - doesn't use 12v power...nor does system RAM
    1-2 Hardrives - 2-3amps each to spin-up at boot and 1-2amps each thereafter
    2 CD-RW/DVD 1-2amps each
    2 Case Fans .5-1 amp for both

    So lessee...if everything is running full bore at once it would need about 30 amps of 12 volt current. But no software application maxes everything out at once. Your peak load levels while gaming or benchmarking are going to be in the low 20's amperage. So you need a unit with at least that. Power supplies are more efficient and last longer when they are ran at 50-75% of their total max capability so just how much overhead for that you want is your call.
     
  12. Trigunflame

    Trigunflame Member

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    Thanks again for All of the answers, this is really helping me out.


    BTW it seems hard to find PSU that have anywhere near 25amps on a single rail, does anyone have any links that I could follow for some?

    http://www.newegg.com/Product/Product.aspx?Item=N82E16817194019

    For example, ENERMAX Galaxy EGX1000 states: +3.3V@30A,+5V@30A,+12V1@24A,+12V2@24A,+12V3@24A, +12V4@24A,+12V5@24A,-12V@0.6A,+5VSB@6A according to this it doesn't even come out to 25 amps..

    I'm going to continue browsing around and hopefully come across some more myself.
     
    Last edited: Jun 13, 2007
  13. Makalu

    Makalu Ancient Guru

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    There's only a handfull of multi-rail units that have any single rail current limit of 25 amps or more. Most are rated at 18-20 amps since the whole purpose of splitting up the rails into current limited branches is to keep the maximum amperage down for safety reasons. Just to clarify, when a graphic card manufacturer says they recommend a unit with, for instance, 12volts@30amps ...they are talking about the maximum combined output...not the individual rail current limits.
     
  14. Trigunflame

    Trigunflame Member

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    Thank you, that statement right there cleared up every doubt I had with this stuff; believe I can finally make my purchases now.
     

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