Why is the PSU often under estimated?

[bryanl]

I would think it is a good idea to get something at least gold rated?
i went with platinum but was wondering what determines how good a PSU really is?

Platinum and Gold are efficiency ratings, not reliability ratings, but in practice the higher selling prices of Platinum and Gold power supplies means they tend to be more reliable due to use of better components, including the Japanese capacitors Torn Mind mentioned.

 

[philipma1957]

GPU manufacturers overstate their PSU requirements because they don't know what quality PSU you are using, or what other components you have in your system.

There are two other problems: 1) a lot of (particularly cheap) PSUs don't actually output the wattage they're rated for. 2) All PSUs get "tired" as they age and are able to put out less overall.

An i3 rig and a GTX 780 with a single SSD, at stock voltages and speeds, will probably run on a 400w PSU no problem. But if I'm adding that same GPU to an aggressively overclocked, fully kitted out gaming rig, I could be using 600w of power before I even drop in the video card.

A lot of people don't know why a psu gets tired over time. Has to do with the capacitors . Caps are like rechargeable batteries they have a life and every charge/ discharge cycle ages the cap.

I used to build a lot of amps for music. I purchased many high power caps to build the amps. I knew that I had received really fresh caps if I turned off an amp while the cd/radio/tv was still playing . If the cap was really fresh you could hear music for 20-40 seconds as the fresh cap was discharging its power. In time the 20-40 seconds of after music would drop to 10-20 seconds then 5 -10 seconds. then 0-5 seconds. I would know the caps were aging.

 

[pauldun170]

Let's use a Evga GTX 780 i ordered for a example, They(evga) say too use a minimum of a 600 watt PSU? is this wrong? or is it just a recommended rating?

Max power draw of 250 from card
then you take...
1. Worse case scenario of PC configuration (additional components drawing power in addition to worst case processor drawing power)
2. Worst case PSU (crap efficiency, crap deliver characteristics)
3. Buffer zone

GPU makers want best user experience possible and if they can mitigate risk by recommending a hefty PSU then all the better.

 

[theAnimal]

A lot of PSU'd dont put their so called "indicated power" to a single 12V line. They put it to a combination. And thats why you have a difference in PSU's. Read the indication sticker carefully, you will see good PSU's having the indicated power all delivered to a single 12V line and other having less power to 12v lines and indicating a combined mode. Thats why a medium heavy GPU can run on f.i on a 400W Seasonic PSU and not on a cheap 400W PSU. I am not talking about efficiency here. Purely output power to a single 12V line.

A good quality PSU can have 1 or multiple 12V rails, it makes no difference. See the sticky for more info.

 

[JBT]

Most newbs just buy any ole PSU, Most New DiY builders buy WAY over what they need. Walking around the PSU area at a place like MicroCenter is an interesting experience with folks having single 7950's etc thinking they need to buy a 750 watt psu, and then having the sales guy up sell them to an 850.
In some cases I get it though, especially if you are ever going to go dual video card. I like having the option in the future..

 

[BonzaiDuck]

I mean the Seasonic Platinium and Gold series. The G series have true 12V power also and are not so expensive and have 1 of the best low load efficiencies(75% at 22,5W),the 660W Platinium also(76% at 22,5W).

I think a lot of us favor Seasonic, and some like myself tend to do it now because we're lazy about searching for more recent comparison reviews.

If the reviews are done well under serious lab testing, there will be a relative assessment of voltage ripple and other electrical factors. This tipped me toward Seasonic back in '07. I'm sure, by now, that other PSU makers are trying to improve their products.

Generally, some published magazine PSU power-guides had noted that warranty-period mattered more for this item than other components, and many have suggested that the weight of the unit says something about its quality. These ideas are at least six or seven years old.

Then there's "picking the right wattage." Many of us use the "Extreme Outervision PSU calculator." You simply go down the list, select processor and motherboard type, input your overclock expectations, SSDs, hard disks, optical drives and myriad other facts, and it generates a result.

But the result assumes that your system is running full-bore at load, with draws by all the components at peak simultaneously. When you add in other components you don't plan on buying right away -- just to make accommodation for "expansion," the calculator gives you an even higher result in watts.

 

[lehtv]

But the result assumes that your system is running full-bore at load, with draws by all the components at peak simultaneously. When you add in other components you don't plan on buying right away -- just to make accommodation for "expansion," the calculator gives you an even higher result in watts.

No, the default setting assumes 90% load, and you can pick whatever load you want for the calculation, in 10% steps

 

[BonzaiDuck]

No, the default setting assumes 90% load, and you can pick whatever load you want for the calculation, in 10% steps

My misunderstanding, then . . . :\

 

[bgt]

A good quality PSU can have 1 or multiple 12V rails, it makes no difference. See the sticky for more info.

I've read it. But is it not better to have 1x 12V conversion(going to multiple 12V output lines) from the mains + using DC-DC convertors(from this 12V line) for the 5 and 3.3 V lines(Seasonic) then having multiple 12V lines + 5V and 3.3V line conversions from thew mains?

 

[piasabird]

If you look at technical data on a power supply they show a curve that flattens out when it reaches about 75% of its rated capacity. The closer you get to the capacity, the less efficient it is.

That being said, I used a CX430M power supply for a computer with no Video card and I doubt I will use much over about 160 watts during normal use. 300 watts would have been enough. However, a lower capacity power supply often has fewer options on the number and selection of connectors.

 

[theAnimal]

I've read it. But is it not better to have 1x 12V conversion(going to multiple 12V output lines) from the mains + using DC-DC convertors(from this 12V line) for the 5 and 3.3 V lines(Seasonic) then having multiple 12V lines + 5V and 3.3V line conversions from thew mains?

This is arguably the best PSU available and it has multiple 12V rails.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=352

 

[Z15CAM]

Compare the $270 Antec HCP-850 Platinum 850W to the $135 BEFX KM3 XFX Pro 850W Black Edition for 1/2 the price ;o)

 

[lehtv]

At least compare platinum to platinum instead of gold... and the hcp-850 plat costs $225 on newegg. It's still horrible value for money though, especially considering newegg states it has 3 year warranty

 

[PhIlLy ChEeSe]

Considering you have spend a bundle on a 780Ti I would not skimp on the PSU. I recommend this Seasonic KM3 designed 750W unit from XFX: http://www.hardwaresecrets.com/prin...Edition-Full-Modular-Power-Supply-Review/1695

And if you plan to SLI the 780Ti go for the KM3 BEFX XFX 850W Pro Black Edition although the XFX 750W BEFX Pro Black Edition would probably handle it.

yeah
You bought a top of the line GPU then only buy a silver rated PSU?