PSUs what do you know?

stickroad

stickroad

stickroad

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Hey guys, the one piece of hardware that most people misunderstand i think is a Power Supply (PSU) including myself. Maybe im wrong but from what i gather from the Spec checks, most people have put in a PSU that is much higher rated than they actually need.

So if i spec a person a pc weather that be someone from these forums or someone that i know in person, i want to make sure 100% that the particular power supply i have chosen will be plenty of power. If they question it i would like to confidently tell and explain to them why it is plenty of power and give them a bit of insight how PSUs actually work.

If someone would be so kind to explain or even give me a link to a website that explains what you should look for when picking a PSU, explain how the Rails work etc....

I would be very great full.
 
What do you mean how do PSUs actually work? I probably couldn't explain how they convert from 230AC to a level that your computer can use but frankly it is unimportant to most.

For a PSU I'd generally look at the 12V - how many Amps it has (or on 12V multiple rails if that is the case), you can check the 3V and 5V rails but if the 12V is ok then the others generally follow. Rails can be either split, single or some combine to be single if any one rail is overloaded.
Look at the sustained output, the max doesn't tell you too much.
Reputatable brands are important as are warranties.
If you can pick up the PSU physically then heavier weight tends to be a rough approximation of quality - if I was a manufacturer I'd put bricks in my PSUs. ;)
Modularity can be a nice feature but isn't strictly necessary and does add an extra layer of complexity as a failure point.
Price is often, but not always, indicative of quality.

Those are a few of the things I look for when judging PSUs. :)
 
semi-pro waster said:
What do you mean how do PSUs actually work? I probably couldn't explain how they convert from 230AC to a level that your computer can use but frankly it is unimportant to most.

For a PSU I'd generally look at the 12V - how many Amps it has (or on 12V multiple rails if that is the case), you can check the 3V and 5V rails but if the 12V is ok then the others generally follow. Rails can be either split, single or some combine to be single if any one rail is overloaded.
Look at the sustained output, the max doesn't tell you too much.
Reputatable brands are important as are warranties.
If you can pick up the PSU physically then heavier weight tends to be a rough approximation of quality - if I was a manufacturer I'd put bricks in my PSUs. ;)
Modularity can be a nice feature but isn't strictly necessary and does add an extra layer of complexity as a failure point.
Price is often, but not always, indicative of quality.

Those are a few of the things I look for when judging PSUs. :)
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Thanks for that Semi.

Sorry, what i said about how do PSUs actually work, that wasent really the right way of saying it. I just basically meant, how the rails actully work, so what do you look for in the rails. Sorry bit of confusion on my part, my bad. :p

Thnaks again Semi.
 
I remember reading somewhere that when building a system, you should allocate 10% of the total budget of the hardware in the PC Case to the PSU, ie if mobo, CPU, Ram Graphics, HDD, PSU, optical devices, soundcard, PC Case etc came to total price of £1000, then you should allocate £100 for buying a PSU.

I know that this doesn't actually enlighten anyone on how PSU voltage rails work, but I thought it was a half decent bit of advice from the financial point of view. :)
 
jbloggs, that is pretty sound advice although with the slight caveat that once you get much over £1,000 the law of diminishing returns starts to hit with a vengance, e.g. a Corsair HX 620w at ~£100 will cope with pretty much any system that you buy until possibly getting into phase or very large servers with stacks of hard drives etc. :)
 
Any questions i ask, do you mind referring to the Corsair 520 PSU please. http://www.overclockers.co.uk/showproduct.php?prodid=CA-005-CS&groupid=701&catid=123&subcat=823 :D

semi-pro waster said:
For a PSU I'd generally look at the 12V - how many Amps it has (or on 12V multiple rails if that is the case), you can check the 3V and 5V rails but if the 12V is ok then the others generally follow.
Click to expand...

Whats the minimum Amps a 12V, 3V and 5V Rails and the +5vsb Rail should have, before you decide that particular PSU is not the right one? Overall not just say on a individual component, like a GPU.

semi-pro waster said:
Look at the sustained output, the max doesn't tell you too much.
Click to expand...
Where in the Corsair 520 Specification would i find this?

If a PSU has triple 12v Rails this is much better than a PSU having just one (if PSUs even have one)?

On the Corsair website it has 12v1 12v2 and 12v3 im guessing these are the triple rails, their is also one more called -12v what does this stand for?

The Corsair has a combined rating of 40A, is this worked out by adding each rail together? On the Corsair website it has the specs and i cant work out how they are giving adding the rails up?

Thanks guys, this is really helping me out. :D
 
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stickroad said:
Whats the minimum Amps a 12V, 3V and 5V Rails should have, before you decide that particular PSU is not the right one? Overall not just say on a individual component, like a GPU.
Click to expand...

Generally I'd say you should be looking for 30A on the 12V rail (or at the minimum spread across the rails if multiple and remember it isn't a simple additive formula e.g. 18A+18A = 36A, it is more like 30-32A normally) and around 15-20A on the 3.3V and 5V rails.

stickroad]Where in the Corsair 520 Specification would i find this?
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The Corsair product page has the information in this case and it will also usually be on the label stuck onto the PSU. Although oddly here they claim 3x18A equals 480w and that it also equals 600w on the 620w unit so they must be using some kind of limiter for the 520w version I'd guess. Actually you are more looking for a label saying "max load" or similar which is often displayed on cheaper PSUs, if they don't have that then in theory they should be capable of their rated output at all times.

Efficiency bands are another point to consider, many PSUs now are 80%+ efficient but if you are going to be loading a PSU very lightly then you might want to consider a PSU with a lower rated capacity e.g. at the extreme end of the scale going for a 1kw PSU for a system requiring 200w is probably going to be less efficient than going for a 400w PSU - this assumes both PSUs have efficiency peaks around 50% load.

stickroad said:
If a PSU has triple 12v Rails this is much better than a PSU having just one (if PSUs even have one)?

Thanks guys, this is really helping me out. :D
Click to expand...

Single rail units can be better for dual graphics card systems as sometimes the system can be a little touchy about the PSUs it uses. The Corsair is actually a single rail unit in effect as explained in the JonnyGuru review although he explains it better at the end of the 620w review because if one rail is overloaded there is no limit on it so all 'rails' can combine.
 
So whats an example of a poor 12v rail and an example of a good 12v rail?

(sorry to dig up a really old thread but i've always been curious and was just wondering how decent my own PSU is)

- +3.3V(36A), +5V(30A), +12V1(18A), +12V2(18A), +12V3(18A), +12V4(18A)
 
From the specifications given it looks pretty decent, all the rails are rated pretty highly in Amps. Knowing who makes it would help with clarifying how good their reputation is but if the PSU is stable and causes no errors then it as decent as it needs to be. :)
 
semi-pro waster said:
From the specifications given it looks pretty decent, all the rails are rated pretty highly in Amps. Knowing who makes it would help with clarifying how good their reputation is but if the PSU is stable and causes no errors then it as decent as it needs to be. :)
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Its an OCZ 600w, just got it last week for £45, thought it was a bit on the cheap side, but all i could afford.

3 year warranty.

I assumed it was decent, no real complaints or warnings, but really i just wanted to know a bit more about them, hear so many people talking 12v rails and haven't a clue what it meant. So its the ampage on the rails you look out for? So 18 is high? Whats a low example?
 
18A on its own isn't very high but you have 4 rails each at 18A apparantly, as I've said above it doesn't simply combine to give you 72A, the total will probably be more like 62-64A which is more than enough. There is a formula to work it all out exactly but I'm afraid I can't be bothered and I can't remember the sums offhand anyway. The headline figure of Amps is helpful as a rough guide but you need them to be stable, you need the PSU to be built well (which usually equates to quite hefty with the heatsink etc in it) and perhaps most importantly, but least often used is that the PSU won't take your other components with it if it dies.

OCZ make decent enough PSUs, I wouldn't rank them in the top tier - Corsair (rebadged Seasonics or at least some were), Enermax, Seasonic, Tagan but they are solid enough.
 
semi-pro waster said:
18A on its own isn't very high but you have 4 rails each at 18A apparantly, as I've said above it doesn't simply combine to give you 72A, the total will probably be more like 62-64A which is more than enough. There is a formula to work it all out exactly but I'm afraid I can't be bothered and I can't remember the sums offhand anyway. The headline figure of Amps is helpful as a rough guide but you need them to be stable, you need the PSU to be built well (which usually equates to quite hefty with the heatsink etc in it) and perhaps most importantly, but least often used is that the PSU won't take your other components with it if it dies.

OCZ make decent enough PSUs, I wouldn't rank them in the top tier - Corsair (rebadged Seasonics or at least some were), Enermax, Seasonic, Tagan but they are solid enough.
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Yep thats the big frightener. I had a 400w Antec which came with my Antec Sonata II which never missed a beat, but with a major upgrade i thought i'd get some decent power under the hood for it to cope better with, and lessen the risk of an explosion.

The Antec was probably good enough, but i got £25 for it anyway. :D
 
The reason why heavier people say about qualility is due to how it is made being basicaly a transformer (with a bridge rectifier to produce a smooth DC output well smoother and smooth as they can) The heavier the transformer the more windings it has which means better transfomer as the current will cut the windings more. Basicaly this is true. Im an Electrician, hence I know this usless info.lol
 
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