PSU Questions

Discussion in 'Hardware Discussion & Support' started by IEMC, Jan 20, 2008.

  1. IEMC

    IEMC Neighborhood screw up.

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    I'm not a knowledgeable guy when it comes to PSUs, so I have some questions.

    1. When a PSU has more than one rail, do you add up the amps to get the amperage for that PSU?

    - Scenario: I have a graphics card that requires at least 22 amps on the +12 rail. The PSU has 2 rails, both at 16 amps. Would the graphics card work with this PSU? Total, the amps is 32, so I'm wondering if that's how that works.

    2. What are good brands of PSU to consider when purchasing?

    3. This deal is so tempting for me, is this a good PSU?
    Newegg.com - COOLER MASTER eXtreme RP-500-PCAR ATX from factor 12V V2.01 500W Power Supply 110 - 115V/220 - 230V Nemko, TUV, cUL, CE, BSMI, FCC, CCC - Retail

    Do you think this would run my setup? (see PC profile)

    Thanks a bunch.
     
  2. OldBuzzard

    OldBuzzard DH's oldest Geek

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  3. Skull

    Skull <b>Boney Admin<b>

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    yeah I agree with old buzzard, hell of a PSU.
     
  4. IEMC

    IEMC Neighborhood screw up.

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    Sorry if I come off as rude but: I didn't ask for opinions on other PSUs, I simply wanted to know if that PSU I picked out is good enough.

    I picked it because of the price and the name brand on it. I know Cool Master is a good brand, and for 10 bucks after rebate it's almost a steal. I just wanted to know if the amps are good enough as I don't know how dual rail PSUs work.

    Please, just let me know if the PSU will run my computer fine. My GPU requires 18 amps, so I don't know if it's compatible.

    And please answer the questions.
     
  5. Teme

    Teme Super Moderator

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    7300 GT needs 18A :w00t:
    Well the 12V rails has 16A on them so it's not looking good if that GPU really needs 18A.
     
  6. IEMC

    IEMC Neighborhood screw up.

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    Is that how that works, though? You don't combine the amps to see if it works?

    That's wierd, though. As I know, like, 8800's need ~28 amps. Then I see people with PSUs that have multiple rails with only about 20 amps on each and they run it fine.

    Correct me if I'm wrong.
     
  7. Dyre Straits

    Dyre Straits 10 Grandkids -2 Great-grandsons

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    I would suggest that you re-read question #2 in your first post then. You certainly DID ask for opinions on other PSUs.

     
  8. kris23

    kris23 Going Insane.....

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    man if the 7300 actually uses 18A i would go over to one of nvidias labs and slap them all......

    the only way to calculate the amps of a multirail PSU is to see the watt output on the 12v rail and figure out how much it is..... (12 x A = 950w) is an example volts times amps = watts....

    and if you cant figure out how to use that formula..... that aint good lol

    i like single rail PSUs better

    EDIT: lol Dyre owned you man....
     
  9. IEMC

    IEMC Neighborhood screw up.

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    I realize I said that, but I was only asking for the names of the company, not actual products. But whatever.

    And kris: Alright, I understand what you're saying, but with that calculation (just taking the total watt output) it's also considering the watt outputs of the 3.3v rail, and the 5v rail, etc. Should I take those rail's watt outputs, take it away from 500, then take that difference and divide by 12 to get the combined amp output?

    I think that made sense.

    EDIT: After doing what I said, I got a combined amp output of the 12v rail to be 26 amps, which makes sense after reading around on how dual 12v rails work.

    That's more than my current PSU's amps, it's a name brand, and it's gotten tons of good ratings on fairly high end machines, so I'm sure it can run my computer, right?
     
  10. Zelig

    Zelig Well-Known Member

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    That PSU should work. For multi-rail PSUs, amperage rating doesn't refer to a what a single rail can output.

    However, amperage from different rails can't be added straight together to give a total, the total combined +12V output is usually lower than the sum of each +12V rail.

    That's combined output if the +3v and +5v rails are fully loaded. Even if they're empty, the +12V rails probably can't combine for 32A. Higher end PSUs tend to have more information on their spec sticker, detailing what the combined maximums are.
     
  11. cozumel

    cozumel I'm dangerous but cute...

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    1. You don't add the rails up for total amps. I do not have enough knowledge to advise you. We have a super-mod at DriverHeaven who does all the PSU reviews and you could PM her for a full run-down.

    2. This list isn't complete and is merely off the top of my head: Antec, Enermax, Thermaltake, Hyper, Corsair, OCZ

    3. The cheapest I have found from a reputable brand and gives enough amps that you have specified is the Enermax EG495AX-VE FMA. Try and find a review on it somewhere. It has 22A on both rails and is $40 after MIR.
     
    Last edited: Jan 20, 2008
  12. kris23

    kris23 Going Insane.....

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    you only use that formula for the 12v rail, as thats the only one thats important......

    i'd do the calculations but im too lazy....
     
  13. cozumel

    cozumel I'm dangerous but cute...

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    And you could use the PSU calculator which is stickied at the top of the forum. I think the lite version is free but does not take amperes into account but the pro version does. I think a 7-day subscription to the Pro version costs just $1.
     
  14. IEMC

    IEMC Neighborhood screw up.

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    Could you do it, please? I need to know if this PSU is a viable idea.

    At least check my math. It seems like 26 amps is the correct number for the total.
    I also just emailed cooler master, hopefully they'll get back to me soon. I wonder if they're off tomorrow.

    I'd use the PSU calculator but I have no way of paying for it. Besides, if I end up wanting to buy this, I need all the money I can.

    I'm short on cash. I have exactly enough to buy this and a few other things. Cant stretch any further.
     
  15. geraldmango

    geraldmango New Member

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    Its not the only thing you are short on. Manners would be another one high on that list. You asked questions and they were answered, so in future sort yourself out when you post publically on the forums otherwise the mods will not be too nice.

    That coolermaster PSU is entry level, if its the only thing you can afford then you have no option or you could wait and save a bit more to get something good. My friend has that PSU and its loud as hell and has some cheap ass components inside it, but what do you expect for $40? Only way you are going to know for sure is to try it as all the PSU calculators in the world and advice will never give you a 100% answer as every PSU has different quality of components inside and even those some claim high amps on 12v rails they will not be stable and could cause BSOD's, restarts, the works. Take into consideration the variety of components in a system and no one on this forum will know for sure.

    Also bear in mind if you buy that PSU and it works, it wont give you any room for the future so its effectively $40 out the window. (or $10, whatever).
     
  16. kris23

    kris23 Going Insane.....

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    25.83A roughly
     
  17. IEMC

    IEMC Neighborhood screw up.

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    This is true and was one of the first things I also considered.

    It's not necessarily an upgrade or a future prood, though, but more of a fix for this freezing issue I've been having (see the "freezing question" thread in this forum section), and I suspect it's the PSU. Since it's only 10 dollars after MIR, I thought it was a good deal for my situation.

    It's also replacing my cruddy, generic, PSU I currently have, anyways. That's always a plus.

    I would wait and buy one, but I don't plan on upgrading until I get a job, which may be awhile from now. When I do upgrade, though, I may replace a majority of my parts, so a new PSU is imminent, anyways.

    In my mind I keep going back and forth between buying this for (eventually) only 10 dollars, or keep the same PSU and wait til I get a job, then buy something semi-future proof or something high end. I don't know anymore.

    Thanks for the input.

    About the same as I got. So it's more amps than my current PSU, too, which is good.
     
  18. kris23

    kris23 Going Insane.....

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    yea it works.....
     
  19. IEMC

    IEMC Neighborhood screw up.

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    Alright, I think I may order it, along with 2 120 mm fans for the side of my case.

    Total of 50, after rebate it's 20.

    Thanks for all of the input, peoples.

    Once I get it I'll let you guys know if it works out.
     
  20. kris23

    kris23 Going Insane.....

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    alright.
     

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