Power supply. does wattage matter?
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Thread: Power supply. does wattage matter?

  1. #1
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    Power supply. does wattage matter?

    Hi
    My friends desktop computer power supply has a problem?
    I told him he has to buy a new power supply.I also told him he has to buy a power supply with same wattage and amps.am i correct?
    does it have to be same wattage? what happens if it is lesser than the original power box wattage? is there a particular minimum and maximum wattage for a particular hardware configuration?
    Thanks

  2. #2
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    hmmm...

    Not necessarily, although you should never go DOWN in wattage from the original, anything bigger should be fine. And yes, there are some general guidelines for reasonable expectations. If you can provide specific system specs, we'll try to advise you more specifically, but in general, 350 watts or more for a modern PC is normal. If you have two hard drives, two optical drives, and some additional case fans or USB devices, 400 watts or bigger would be a good idea.

    Cost aside, you can't have too much power.
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  3. #3
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    Yes it does matter.

    Depending on what hardware he has then obviously the more he has the more power is required from the PSU.

    On a typical system, personally i wouldnt go under 350w.

    Also if a new PSU required, dont get a cheap one.

    If you get a cheap one it wont last long and will cause you problems.

    I would go with Enermax or Antec PSU's
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  4. #4
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    Thank You Gentlemen.It makes sense.What would happen if the wattage is less? Some devices won't come on?

  5. #5
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    You will find that if there isnt enough power to go around then yes thing wont work, and can actually be harmful, and you will notice more and more reboots without warning.
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  6. #6
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    Unpredictable, unreliable, virtually undiagnosticable problems. Simply don't do it.
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  7. #7
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    Heh, heh beat you to it this time Shiva
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  8. #8
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    It's worth spending the extra on a good make of power supply. Cheap PSU's often don't give anywhere near their rated output and can have unstable voltages too. I like Antec or Enermax.

    http://www.tomshardware.com/howto/20040122/index.html

    http://www4.tomshardware.com/howto/2...pplies-05.html

    http://www4.tomshardware.com/howto/20030609/index.html

    http://www4.tomshardware.com/column/20011012/index.html

    http://www.anandtech.com/showdoc.html?i=1774

  9. #9
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    Allright.Now i have enough to enlighten the hardware store guy who said voltage doesn't matter.
    Thank You once again,all.
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  10. #10
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    Here's some Tech Info on Power Supplies:

    Power =E x I

    Power in Watts
    E is the Voltage
    I is the Current

    Most good power supplies list the voltages and the max current.

    So if you measure all Voltages and Currents in your system,use the above Formula, add them up, you'll then be able calculate the Total Power of the Unit you need.

    An added side note: If current Increases and voltage stays the same, the Power Increases and Heat Increases also. What this means is that most P/S have decent Voltage regulators, and the load increase or decrease is what causes the current to increase or decrease, therefore the power does the same.
    Last edited by irdreed; April 22nd, 2004 at 12:03 PM.

  11. #11
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    A minor point for sure, but realize that psu's also have minimum load requirements. In other words, they have to have a certain amount of power being drawn from them for it to regulate properly...some will refuse to turn on. This oftens throws some people off when they disconnect a lot of components in order to test another. The4 psu doesn't turn on, so they think they fried it.....add another component onto it and it works.
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  12. #12
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    Bistro, I understand the concept, but have never heard this before. Is this minimum generally posoed on the label of those PSU's that require a minimum load to run?
    If life was simple then it would be no fun.

    Regards, Mike

  13. #13
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    You will sometimes find it on the specs label; if not, it may be on the specs sheet inside the box or on the box itself. The good quality psu's will just shut down completely if the power draw drops below minimum load; poor quality psu's can actually be damaged if that happens, believe it or not.
    I can't count on all my fingers and toes and ears how many folks I've helped in the past who went out and bought a bunch of super whiz-bang components, but then bought some psu with a name like "BurnOut Industries Finest", "HongKong Back Alley Special", "The People's Power Supply", "Maybe or MaybeNot", etc. and ended up ruining their computers. A good power supply should be right up there with the same consideration as one would give the processor.
    Last edited by bistro; April 22nd, 2004 at 05:16 PM.
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  14. #14
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    I have a great appreciation for good quality power in sufficient quantities as I replaced the 250w PSU that came with my computer with a 480w Antec. This was triggered by the purchase of a high end (at the time) video card and the anticipation of ultimately replacing most of the components over time. I have now replaced everything but the keyboard and am looking at possibly buying a Radeon 9800 Pro to replace my Ti 4200. Newegg has them for $200. In any case, power is not something I worry about right now.
    If life was simple then it would be no fun.

    Regards, Mike

  15. #15
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    Also FYI: A pentium IV, Athlon XP and Intel require a minimum of 12 amps on the 12 volt side. Even a 400Watt PSU can have lest then 12 amps on the 12volt side, and she will not boot. I have learned that from erpierence.
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