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What's the obsession with PSUs?

Discussion in 'General Hardware' started by silkstone, May 4, 2009.

  1. silkstone

    silkstone

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    OK after seeing so much (bad in my opinion) over PSU's i thought i'd ask other members what they think.

    In my opinion there are 3 things you should look for in a PSU.

    1 - Manufacturer # you need to get a PSU with a recognized name or from a decent OEM manufacturer. If you can get a 80% efficiency one even better as it'll lead to less heat in the system and lower energy bills, but it isn't essential

    2 - Amount of rails # If you can get a PSU with a single 12v rail, at most you ant 2 rails. the only time you should get a psu with 4 rails is if it's rated over 1000w.

    This is just common sense. say you buy a 550 w psu with 2 rails, you'll probably get 200w on each rail so you could run a single high powered graphic card on each rail, and what is left over is wasted.
    If you just get a 450w power supply with a single (1) rail, you will be getting somewhere around 350w on that rail, allowing you to share all that wattage over maybe 3 high powered graphics cards. I guess this isn;t a given, as there are some graphics cards that will use in excess of 150w, but at the least you'd be able to run 2 graphics cards - the same as the 2 rail psu

    3 - Total wattage # You need to think about how much power your computer really needs, and then buy a PSU maybe 200w over that value to allow for future upgrades.

    I don't understand why people are giving advice to other members to buy 750w PSU's when the person's rig would only use 400w max. They don't even consider the other aspects you have to consider when buying a PSU.

    My rig uses a 550w (max rated) PSU with 2 rails, i can get about 175w off each ao i can run the mainboard/cpu on 1 rail, and my 4850 on the other. The amount of times i've been told i should upgrade my PSU is unbelievable. I don;t see any reason to upgrade until i go xfire.
    (btw AcBel is an oem manufacturer that produce psu's for Coolermaster)

    "In the real world, very high PSU ratings are seldom important. If you're not running giant drive arrays, big Peltier cooling rigs and/or an amazingly overclocked CPU, a quality 350W PSU should be more than enough for any system. Extra capacity doesn't hurt, though; a computer that only needs a 300W PSU won't draw any more power if you give it a 600W one." - Inside your PSU http://www.dansdata.com/psus.htm
    Last edited: May 4, 2009
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  2. Flyordie

    Flyordie New Member

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    Mine uses 4x12V rails and they are all dedicated. 18A each rail. Max load combined on the 12V rails = 41A. Thats on a 550W PSU. The rails are also marked on each lead.
    CPU gets 1 rail.
    Mainboard gets another which includes all the PCIe slots ect...
    Each of the 2 PCIe connectors on the PSU gets its own rail with an equal # of Molex and SATA leads on each of those rails.

    Good balance imho. So I agree for the most part.. you don't need to upgrade your PSU just cause it may seem underpowered.
    I ran this setup in my specs on an EA380 for 2 weeks and it did good.
    silkstone says thanks.
  3. HellasVagabond New Member

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    Manufacturer ( Enermax, Seasonic, CWT, PC Power And Cooling, E-Power and a few more ) , Rails ( Usually the more wattage the better the rails ) , Capacitors ( 120 Celcius ones are usually the best ), Power Output ( According to your needs although anything over 850W is considered futureproof ), Noise Levels ( If you can get a PSU with sub 40dBA noise levels in Load that would be great ), Warranty ( 5 Years are considered to be the best offer out there ).

    Thats what everyone should look when searching to buy a power supply, at least that is my opinion on the matter.
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  4. r9

    r9

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    That is very smart question. If a tell you that in the store that I work in the galaxy far far away we use 12 eur PSU on midrange computer and guess what they don`t burnup.
  5. silkstone

    silkstone

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    That seems like a decent enough PSU. Total of 4 rails x 18A = 72 A. but max rating of 41 A Leaving a lot of room variable power on the other rails. I.e you could run your CPU at 8A, or maybe 10A for an overclocked quad, leaving at least 30A on the other 3 rails for Xfire HDD's or whatever.

    I doubt they ever will as thay aren't being overclocked so will probably only use around 5A on 1 rail and even a high powered video card would only use 10A - not a huge amount of current.

    Power supplies will generally only go "POP" if your putting too much load on a single rail. I watched the Corsair UTube video and i'm sure they tried to put around 30A on a single rail!

    If i had a cheap PSU and replaced the capacitors with better quality ones - what would the result be?
    Last edited: May 4, 2009
  6. Deusxmachina

    Deusxmachina New Member

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    ? A 2900xt minimum recommended power is like 30a. I think even a 7600GT needs around 18a.
  7. phanbuey

    phanbuey

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    Which is why single rail PSU's are the bomb.
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  8. silkstone

    silkstone

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    I doubt it, from the power equation P=IV (current x voltage) that would equal 216w just for a 7600gt and 360w for the 2900xt!!!!

    {Edit] i forgot those are old cards and probably running on the 5v line - still 30A x 5V = 150w for an old graphics card.
  9. HellasVagabond New Member

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    It should withstand larger power loads and thus bigger temperatures, if the wattage allows it that is.
  10. FordGT90Concept

    FordGT90Concept "I go fast!1!11!1!"

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    Active PFC is a must--vastly improves effiency.

    Modular cables are a must--hard wired cables are more efficent but all the excess cables restrict airflow in the case.

    A PSU for a system should never run at under 20% load and should never exceed 80% load.

    Power supplies run most efficiently at 50% load and at temperatures lower than 50C.

    Don't bother with PSUs that didn't at least achieve 80+ certification. Better yet, try to get a 82+ Bronze, 85+ Silver, or 90+ Gold certified power supply to save on operational costs.

    Wattage is really only used for advertising anymore. The important thing to look at when considering a power supply is the amperage of the rails. How much amperage you need depends on machine specs.

    Multiple rails aren't necessarily a bad thing. More often than not, they are all combined into a single rail internally. They simply break it in to multiple rails to better control the voltage (more stability) and limit damage should the PSU fail.
    WarEagleAU says thanks.
    Crunching for Team TPU
  11. silkstone

    silkstone

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    Some good tips, You're right about the rails. but i believe there are some PSU's where the rails aren't linked, which is bad. Those would generally be the cheap but high powered chinese ones.
  12. HellasVagabond New Member

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    Expensive power supplies feature Active-PFC, it has been around for almost a decade so it is not something revolutionary.
    Modular cables are a must ONLY if you have low power demands. If you have multiple HDDs, Fans, VGA Cards then you always use all of the cables ( or almost all ) so it matters not if it is modular.
    90+ Gold are the most expensive power supplies in the market and from what i recall there most be just a couple of those available.
    Wattage is never for advertising purposes alone, it always matters but the rest of the power supply must have the quality needed to support that wattage output, there i agree.
  13. Paulieg

    Paulieg The Mad Moderator Staff Member

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    I think the specs to look for are well documented here. The obsession with psus is because the PSU IS the foundation to your system. That cannot be stressed enough. No other component in your system has more of an impact on stability, nor is there any other component that can kill your computer like a bad PSU. For this reason, people are obsessive. Are people dramatic about it? Possibly. The reason for this is because there have been way too many posts where people are trying to run very expensive and power hungry components on low power, generic supplies with potentially unstable rails and power spikes. People by nature are dramatic when attempting to get an important point across.
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  14. silkstone

    silkstone

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    You are completely correct, but i don;t see the justification on someone advising a $200 850w PSU to someone who would be running a 4870 and core 2 duo. The only way you'd need that much was if you were running an overclocked quad core, SLI/Xfire and wanted plenty of spare watts for the future.
    The rule should be a quality cpu, get the system you want, then however much $$$ you have left over if any put towards getting the bigger PSU. Not blowing 1/4 of your budget on a really high end PSU and then not having enough left to buy high end components to utilize the PSU.
  15. FordGT90Concept

    FordGT90Concept "I go fast!1!11!1!"

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    As a general rule of thumb the PSU should be between 10-15% of the total system cost.
    Crunching for Team TPU
  16. yogurt_21

    yogurt_21

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    I think hellasvagabond hit it on the head when he mentioned the future proofing. I know it is the reason why I ended up getting a kilawatt. does my current rig use anywhere near that? of course not, in fact I'd be surprised if I were using more than 400w full load. but when i bought my psu it was along with apower hungry 2900xt and I was planing to go crossfire. So I wanted to not only be able to support 2900xt crossfire, but also any future upgrades I would be doing.

    of course that never worked out the way I planned and I ended up selling that rig off and keeping the psu; and the way things are going I may never use it's potential but still at the time I bought it made sense.

    It's one of those things that some of us like to be covered on. As paulieg mentioned others come on here with expensive gpu's and cpu's while having a rosewill 500w powersupply and ask advice on why it's not working. for many of us we cringe at such a configuration as they have likely caused damage to their expensive compnents by going cheap on the psu.

    I like being covered and knowing my components are powered by a reliable brand that will last me a while. others may simply choose to upgrade the psu along with the other compnents. It changes based on your preferences I guess.
  17. silkstone

    silkstone

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    Too true, and that's fine if you express it that way. It's the "noooo... don't get a 500w PSU or your computer will explode" advice that gets me.
  18. HellasVagabond New Member

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    It will not explode but a rule that i have found after slicing open countless power supplies is that the more the wattage output the best the overall build quality the unit has, plus the more futureproof the unit is .
  19. ShadowFold

    ShadowFold New Member

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    I don't care what anyone says. I will never skimp on the PSU in any system I'll ever build.
  20. silkstone

    silkstone

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    But why spend more on your PSU than your CPU? you also need to remember the quality of the capacitors in the PSU will degrade over time/use. So maybe your thinking of getting a 850w PSU to last 4-5 years, but in 4-5 years time it will not be anywhere near as good as new. PSU's will degrade faster than any other component in your computer. Which brings me back to hellasvegabonds point, you need a good warranty to as the company would have ensured the PSU had been built to last
  21. ShadowFold

    ShadowFold New Member

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    You're gonna need to spend 100$ on one anyway, why not drop an extra 20$ for a great one?
  22. FordGT90Concept

    FordGT90Concept "I go fast!1!11!1!"

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    Power supplies are the only things I ever consider getting an extended warranty on. One of my Enermax Liberty 620w PSUs and my Enermax Revolution 85+ 850w PSU both have a two year extended warranty on top of Enermax's three year warranty.
    Crunching for Team TPU
  23. exon1 New Member

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    I agree.
    I have a 450W one, but I should have bought a 550W just in case I want to get a new graphics card in the next 3 years.
  24. DaMulta

    DaMulta My stars went supernova

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    I almost say spend 200 on a GOOD PSU and don't look back.

    I don't know HOW MANY PSUs I have simply blown because I went cheap.

    <<<----That PSU has SMOKED HARDWARE(literately) and lived to tell about it, and in fact is still kicking.


    Why would I want to skimp on a PSU that could fry every part in my machine if it went out? The stuff adds up real quick!

    I also say buy the 1k PSU because it eats less electricity. Just because you have a 1k PSU does not mean that it's draining all that power. It eats what you use.
  25. n-ster

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    I feel like buying a 600$ 1.2kw PSU now :D

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