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This is a copy of my PSU sticky that has been up at guru3d.com for a year or two figured I should share it with the forum over here as I see a increase in intrest for new system builders out there and this is important info.
The Be All PSU Sticky!
Ok this is the post you were probably pointed to by us guru's here to give a lending hand in a constant problem we see pop up about power supplies and psu related issues.
You can find your answers here to common questions like:
) What is a good psu for X system
) How do I know my psu is bad?
) What is a good brand psu
) What do I need to look for in a psu
) I am having (insert problem) could this be due to a psu problem?
And various other important related material.
PART I - PSU INFORMATION AND RECOMENDATION SECTION
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So first of all about PSU's what are they?
The PSU (Power Supply Unit) is the very core that every single component of your computer must feed from, supplying the power needed to function to everything in your computer could possibly make this the most important part of your pc not to go cheap on.
Why? well for starters a cheap psu is well known not to perform up to par with its rated specs or die out early. Besides that if they don't do a good job at producing constant clean power it can cause system malfunction like random resets, crashes, and every error under the sun. In a worst case scenario it could even damage some part of your hardware or lead you on a wild goose chase to find a problem in your software or other hardware that doesn't even exist.
So what do you do to prevent all this from happening? Buy a good trusted power supply with enough power to run your entire system with ease and leave you some headroom for upgrades.
Noob Mistake #1 thinking psu power is only important by the WATTS rated on the psu, this is very incorrect. The total wattage is a sum of all the smaller separate values of each "rail" in the psu that run at different voltages. So while one 500w psu might have a 25a (amps) 12v (volts) rail, there might be a cheaper one that catches your eye but with only 10a on the 12v rail which is not safe for any current machine to run at.
Without getting super technical yet, what is the best way to avoid getting a bad psu with improper handling of each voltage rail? Easy getting a good high quality name brand psu, its not even a safe bet to read the ratings on cheap psu's as they are often mis-advertised.
Here are a few reasons why:
There is no "standard" way to rate a psu in terms of its rated power. So in an attempt to take advantage of this, often times cheaper psu makers "selectively" rate there products. This is why often times you will find somebody that has a 400w psu thats having trouble handling a system that barely takes 150w of power vs somebody who has a 300w psu thats running a 350w system fine.
How do they do that you say? and isn't that false advertising? Well sometimes it is! If you take all the power from each rail and add them all up sometimes you will find the total number to fall short by anywhere from 20-40w of power they just round up to the nicest sounding number!
What else do they do you say? Well a good psu can perform its duty and give you full power with a wide range of input voltage from your plug in your wall, say +/- 20VAC. A psu has a much easier time producing the 350w its supposed to at 120VAC which is optimal as compared to say 100VAC that you might be feeding it sometimes due to unclean power from your house, but those cheaper companies don't tell you how good there psu did in "other than optimal" conditions.
A good way to help this is to in addition to a good psu buy yourself a UPS or something similar that has AVR on it (automatic voltage regulator) this will keep the power being fed to your computer nice and clean and really help maintain the life and function of your pc. Voltage drops are common in your house! every time something like a washing machine or refrigerator kicks on it sends a voltage spike through your line if it happens to be on the same line in the house, and even electrical companies just send bad power now and then so its always better to be safe than sorry!
A yet another way a cheap psu company might give a false image of there product is they rate its power output in optimal operating temperature, say soon as you start it up and its running a nice 30-36c but once its on for a bit and up to 45c or more it could lose 10% or more of its inefficacy's!
So take those factors into play next time you think just because the 50$ psu has good stats on it and you think its better than your friends 100$ psu with slightly lower stats. Chances are your very very wrong!
So now that brings me to the recommendations part of the sticky what is a good highly regarded brand that I can feel safe with?
Good PSU Brands
At the high end level for those who plan on running a lot of high power equipment and want to feel safe with a high current draw we have...
) PC Power & Cooling
) OCZ + Tagon
) Enermax
) Antec
) Silverstone
) Hiper Modular Type-R 580W
) Fortron
Some lesser psu's that are good for function and ok for a non-over clocked system or older pc's
) Sunbeam
Good and Quiet psu's
) Seasonic
Keep in mind that some of these brands specialize in higher tier psus and don't have any cheap products while others have a broader product range and may have dinky 50$ psu's ... don't buy the dinky 50$ psu!! you get what you pay for! cheap = cheap.
OK so now you know what brands are good for psu, but what do you look for to know its a good psu?
EFFICIENCY - This is important to the psu because it measures how well it does its job at making that power go from a pc frying house AC current to a usable dc computer voltage. The better (higher) your efficiency the less power from your plug the psu has to use at any given time so thats less of an electric bill for you or you! Also the higher the efficiency the cooler the psu will run this to you means a better performing psu, cooler pc case and room, and also less noise! the hotter the psu gets the more air it needs to stay cool so either more, or faster fans will be built on it to keep it cool. Minimum is 70% but higher is better.
12 Volt Line - This is the most important part of the psu, this is where the most important and demanding parts of your computer take there power from, remember earlier when we said that 350w psu with 10a on the 12v line would suck vs the one with 25a? Well thats because in extreme situations as much as 90% of your total system power could be on the 12v rail on your psu!!! so even if its a 500w psu if only 1/8th of that wattage is 12v then your screwed!
So what do you need?
ViciousXUSMC recommends the following:
For older systems under 2ghz with light equipment 15a on the 12v rail
For Mid-Grade machines with 2Ghz-3Ghz with medium equipment load a 20a 12v rail
For New/High end machines 3Ghz+ or heavy equipment loads 25-30a+ on the 12v rail (go higher for servers or newer video cards lower for more standard setups)
General Rule add about 5a to those measurements if you want to be safe over clocking.
These are my general guidelines and may be higher than you find elsewhere on the net, but here at Guru3d we take pride in our "Rigs" and don't want to take a chance with falling short.
Addon: 12/01/05
In additon to my recomendations there are several online wattage calculators, none of them seem terribly accurate but could give you a ballpark figure here is one that seemed to give me close to correct stats for my system.
http://www.adecy.com/psu/
Remember if in doubt just go higher, it cant hurt!
The psu is the "foundation" of which you computer is built just like your house, you wouldn't want to put all this money into a computer just to have it crumble due to a weak foundation, another reason for the high recommendations is to leave you overhead for upgrading in case you want to add case fans, or lighting, hard drives etc and be safe with it.
So ok now I know the brand, and 12v is important, along with efficiency so anything else?
Yes there is still more!
Here are some miscellaneous factors you need to keep in mind for your personal setup.
1.) Size/Weight - Does it fit? some psu's are bigger and heavier than others make sure your case has enough space to fit it in there! While not always the case another "general rule" is the heavier the better, this being because if its nice and "beefy" it probably means they used nice heavy duty components like heat sinks and capacitor's.
2.) Connections - what cords and power connectors does it come with? the majority of motherboards now are all ATX 12v thus why the 12v line is important but some motherboard require a 24 pin connector vs the older style 20pin, most modern psu's fix this problem by coming with a 20+4 pin power connector that has the standard 20pin with an additional 4pin that connects to it.
It's very important if your motherboard requires a 24pin connector to make sure your power supply has it, in some cases like a DFI Lanparty motherboard trying to use a 20pin with a adapter can cause the board to not work or be unstable!
3.) SLI Certified - A lot of people are going to the Dual video card setup's this would fit in the #3 high end pc with heavy equipment load of 30a or more area from above, so If you want to go SLI do you need a SLI certified psu?? NO! you don't, SLI certification is nothing more than a sticker they get after they pay nvidia some money for to say there psu works with SLI setups, any decent psu listed above will work with sli certified or not, the difference? some may come with the 2 pci-e power cords already attached to the psu, others may require a adapter. Which brings us to...
4.) Dual 12v Rails - This first came about as a "safety" to keep your power levels safe for all your equipment and for yourself (law was passed that not more than 240VA can be passing through any one wire in a computer in case somebody pokes a wire in there and zaps themselves so when psu's got above 20a on the 12v rail (12v x 20a = 240VA) they overcame this by having dual rails thus
why one is 20a usually and the 2nd one is the remainder on a separate rail). But it also served a 2nd purpose, if one part of the system had a heavy load on power (motherboard) so as to not take the power away from the other parts of the pc sharing the 12v rail the 2nd rail supplies separate power to the other parts of the computer. While initially a very good idea and still is, there is one small catch to be weary of! usually in a dual rail setup there is one major rail and one minor rail so a 32a 12v total could be split like 20a on one and 12a on the other. Being perfect for most systems, but in somebody running a 2 7800GTX setup its not perhaps the greatest idea because the minor rail that could be feeding the video cards is not enough power to keep them happy and working properly while the mobo gets more power than it needs. So personally I would stick with a high amperage single rail psu if you are going for a extreme SLI setup, otherwise dual rail is a good choice. (or other option is to find a dual rail psu with high amperage on both rails like a 36a psu would have 20a + 16a which is good or SLI)
Also the rule is just 20a max on one line it doesn't mean they can't play around with it and balance it out and make it 18a+18a for a 36a dual rail psu if they wanted too so it's possible to find a good dual rail psu.
For more details I will quote you this:
Quote:
DUAL 12V LINES: REALITIES
Note that 12V2 is supposed to supply only the AUX12V (2x12V) 4-pin plug, which feeds only the CPU. With PSUs that adhere strictly to the ATX 12V v2.xx Guide, 12V1 then must supply 12V to all the other components that require it. This might lead to a problem with very high power gaming systems that utilize two high power video cards in SLI or Crossfire mode. Current high end VGA cards by themselves can draw >90VA each. Much of this comes from the 12V line via the 6-pin PCIe connector for the VGA card. If you add several hard drives and optical drives, the 240VA limit may be too low. The current ATX12V v2.2 spec was created before dual VGA card gaming configurations for Intel boards were announced. SLI, being an AMD feature that came many months earlier, may have been ignored by Intel's PSU design guide team.
Not all PSUs with 6-pin PCIe connectors follow ATX12V v2.xx to the letter. In fact, they can't, as the guide does not cover the 6-pin 12V PCIe outputs. This connector and its current delivery capacity was specified by nVidia, the originator of the SLI concept. nVidia maintains a list of power supplies that they have certified as being suitable for SLI systems. The question is, Where should this 12V come from? More to the point, which line DOES it come from?
I interviewed a number of engineers from several power supply manufacturers to pose this very question. The answers were surprising. All of the engineers I spoke with wished to remain anonymous. This is a summary of what they told me:
Some PSU makers are using 12V2 to supply more than just the 2x12V or 4x12V connectors. It is often used to power the 6-pin 12V PCIe outputs. Many PSUs marked as having dual 12V lines actually have only a single 12V line â€â€
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