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 Post subject: How much power do you really need?
PostPosted: Mon Mar 10, 2014 12:30 pm 
Smithfield
Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
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Note for mods: I felt this was more appropriate here, but if need be, feel free to move.

So I'm debating about power supplies, specifically how much power do you need? The general rule of late has been that 600W for one video card setups is recommended and add 150W-200W for each video card. However, every time I measure off the wall using my Kill-A-Watt, I get power consumption that's much lower than expected. At the moment, my system with a Core i5-4670K @ 4.0GHz and a GeForce GTX 670 pulls at most 230W. This leads me to believe that I can lower the bar to 450W-500W, assuming the power supply is a quality model. And I put that much since I'm still going on the guideline that a PSU supplying 50% of its maximum rated power is at its most efficient.

I guess this is just a ploy to get people to scrap some money here and there, but the thing with the power supply being a quality model is that it may offset said cost savings. For instance I prefer Seasonic and nobody else now. Their 450W model costs the same as the 650W model about. So why not just get the 650W instead? Well the 650W didn't have the features I need, plus it's an 80PLUS Bronze.

In any case, the thing that I'm not concerned about is the PSU generating heat. I feel it's a rare thing especially since 80PLUS power supplies have made this issue go away even further. For instance, since I have an 80PLUS Gold PSU and it draws at most 230W, it's dumping about 21W worth of heat. A far cry from the 84W my CPU cooler has to dump or the much higher heat my GPU cooler has to dump. And no, heat from resistance is fairly negligible in a given circuit. Resistors used are to fine tune the output and if they're burning up, the circuit design is poor.

IN SHORT: You can go lower than the rule-of-thumb 600W, if the power supply is a quality model.


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 Post subject: Re: How much power do you really need?
PostPosted: Tue Mar 11, 2014 6:09 am 
Thunderbird
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Location: Phoenix, AZ
nVidia recommends 500W.

Everything you said is true. 50% usage is optimal efficiency. But they system will ONLY draw what it needs. If it is not under load that wall outlet will be drawing a lot less. Most systems probably run at about 20% most of the time.

Generally I recommend the Seasonic S12ii 620W because it is only $5 more typically and sometimes actually cheaper than the 520W model and that series overall is almost always the performance/price quality leader. Otherwise I have not really seen advocacy for 600W PSUs as general gaming PSU entry points except that output should drive any uber high end GPU card later if a gamer wants to upgrade their GPU without upgrading the PSU.

So, yes, a super quality 450-500W ATX12V v2.2 or greater PSU would meet your present needs at potentially the same price as a 600W+ quality one. Or you could save money.


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 Post subject: Re: How much power do you really need?
PostPosted: Tue Mar 11, 2014 7:57 am 
Million Club - 20 Plus
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Location: Dixon Springs, TN
Power supply sizing is the big reason I quit posting in the Building Lab. Guys would post their build list and there would be this monster psu in there for 'future proofing'. I would point them to several sites that have/had psu calculators on them and tell the poster that the recommended psu would be VERY generous on the wattage needed and they could go smaller. They would still buy the huge one that they didn't need in the first place.
They'd come here for advice and then wouldn't use it when they got it. Torqued my jaws so much that I quit posting in here about build advice.
I do have to say that the psu in my current setup is much larger than I currently need. But it was a recycle from an earlier build that did need it at the time.


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 Post subject: Re: How much power do you really need?
PostPosted: Tue Mar 11, 2014 8:49 am 
Smithfield
Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
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I'm also wondering just how "safe" it is to push a PSU to say 80% or more. Gamers regularly push their GPU to near 100% with no ill effect on it for years. And I'm sure most of the Folding@Home folks push both CPU and GPU pretty hard. I'm curious since most laptop power bricks that you get will start going 80% or more if you're doing something heavy. And console power supplies tend to run in the 70%-80% as well. The Xbox 360 holds the winner though, with the original SKU running a staggering 97%. Which is weird that it didn't fail before RROD kicked in.

In any case, I wondered if there were sub 500W PSUs that are from quality brands that are cheaper than the what seems to be gold standard Seasonic S12II 620W (normally $70). So I found them: http://tinyurl.com/newegg-psus (cheapest one is a Seasonic 300W 80PLUS Bronze unit for $35)


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 Post subject: Re: How much power do you really need?
PostPosted: Wed Mar 12, 2014 11:12 am 
Thunderbird
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I would not consider those Seasonics in the $30-40 price range worth owning from a quality standpoint. The cheapest PSUs that are of acceptable quality IMHO, are the Corsair CX430 (the consistently best cheapie from warranty standpoint) and Antec Basic series or their VP-450.


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 Post subject: Re: How much power do you really need?
PostPosted: Wed Mar 12, 2014 2:40 pm 
Smithfield
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Seasonic still has a 3 year warranty. At least that's better than most bottom barrel parts.


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 Post subject: Re: How much power do you really need?
PostPosted: Thu Mar 13, 2014 4:12 am 
Thunderbird
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LatiosXT wrote:
Seasonic still has a 3 year warranty. At least that's better than most bottom barrel parts.

Yes, but it will cost anyone around $10 to RMA a PSU under warranty. If you are going to buy cheap, then buy PSUs consistently made of better stuff and better design. [Rock bottom cost Seasonics may fall into that category and could be proposed with collected test article links to back it up.]

While admittedly imprecise and ambitious, Eggxpert has a Tiered list of PSU make/models based upon the dozen or so international computer hardware sites that actually employ a rare $10,000 PSU torture load testing equipment as well as opening up and documenting components and design layout inside the PSU (the list is inside the now very lengthy thread but not conveniently linked).

Tier 3 are acceptable no frills units that deliver rated quality power under specified loads and temps. Tier 4 and 5 are "punt" and "run away, run away" units respectively that have failed.

The list is maintained by a single person (Currently GmsCool) with occasional nominations from other site users based upon a published report or two from one of the rare testing sites that actually test non-manufacturer supplied PSUs and post their testing methodology. It is an impossible list to maintain as makers change unit model family designations for annual marketing, but it is the best (maintained, the only one I am aware of) list I have found where debate breaks out from time to time and units can get downgraded if a maker is found cheating down the road. And only a few handfuls of different PSUs are annually openly examined and potentially destroyed during testing which limits additions.

Otherwise, you are correct, you are limited in evaluating based upon warranty (a good place to start), reputation (user comments), unit weight (heavier still generally is better) and marketing claims that may hint at components and designs used.


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 Post subject: Re: How much power do you really need?
PostPosted: Thu Mar 13, 2014 6:52 am 
Smithfield
Smithfield

Joined: Sun Jun 18, 2006 7:37 pm
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I think without enough of a sample size to actually determine real-world reliability, I can only take what I have in the decision making process.

So unless there's enough of a crowd that says these units blow up all the time, then I'm just going to go with what I know about the manufacturer in general.


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