Power Supply 101: A Reference Of Specifications

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joytech22

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On the other hand, if you plug into a 240 V outlet and have the switch set for 120 V, you can cause damage.
Did that when unboxing a computer, must have flipped the small red switch on the supply and boom, at the Windows XP loading bar the PSU exploded. lol.
 

cangelini

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[citation][nom]cmcghee358[/nom]Did I miss them covering efficiency and the whole 80 PLUS thing?I can't imagine as detailed as it is, omitting something like that...[/citation]

There's still one last part to go!
 

neiroatopelcc

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I wonder how much the power_good signal prevents? is it just the powering of the cpu ?
I recall once using two power supplies to power a sli board and accidently use a molex from the second supply to power a sli power connector on the motherboard - resulting in fans powering up if you powered the second psu even when the first wasn't on (and if you didn't, the geforces would screech due to lack of power)..... maybe that was just the creative yet rubbish asrock board design, but it certainly didn't need a power_good to power up the fans.

ps. "Note: If you find that a system consistently fails to boot up properly the first time you turn on the switch, but that it subsequently boots up if you press the reset or Ctrl+Alt+Delete warm boot command, you likely have a problem with the Power_Good timing. You should install a new, higher-quality power supply and see whether that solves the problem."
Could this explain why I only have 4-6GB memory at post, but 10GB after a quick power off and back on (didn't bother with a reset switch when designing case). Note that 10GB is still 2 short. It used to initialize 10GB - then power off and back on would provide the full amount. Running less than 6GB memory doesn't cause the error.
Someone said I'd have to reseat the cpu, but maybe it's just that rubbish coolermaster power supply?
 

chesteracorgi

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Very informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.
 
[citation][nom]cmcghee358[/nom]But the last part isn't for PSUs. It's just the last part in the series of PC components.[/citation]
covering efficiency and the whole 80 PLUS
If you picked one of these books up you would want the efficiency to move them. Edition 17 was huge and very heavy. These books are already to thick for many to pick up with one hand. Scott Mueller's has published 20 editions of this book and most come with CD/DVD which may guide you to online information about the subject.

Here is a link to his online forum.
http://forum.scottmueller.com/
 

digiex

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I'm just wondering what is the use of the floppy connector...

Until unexpected glitch ruined the flashing if my motherboard, beyond this, I think the floppy connector is useless.
 
G

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I fixed one of those non-compatible Dells way back with a standard PSU. Dell wanted £120 for a new PSU, I was suspicious, "how could they get away with that?". Checked online, found the incompatibility, dodged the bullet bought a PSU for £20 and an adapter for £5. Never bought Dell again nor recommend them.
 

A Bad Day

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This reminded me of a friend who bought a $5 no-name "600 watt" PSU for a +$900 rig.

As soon as he turned on the computer, the PSU failed so badly that it exploded into flames and took out everything: motherboard, RAM, CPU, GPU, hard drive, CD drive, you name it.
 

hunter315

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In other words, it is far better to have a single 12 V rail that can supply 40 amps than two 12 V rails supplying 20 amps each because with the single rail you don’t have to worry which connectors derive power from which rail and then try to ensure that you don’t overload one or the other.
Im quite disappointed to see tom's fell for the marketing BS of "a single rail is better than multiple rails". On a well designed unit it does not matter one bit, the design engineers already split the connectors so the rails were reasonably balanced, and the OCP threshold is set such that added together their theoretical current limit is more than the total limit of the 12 V source so you don't have to have your rails perfectly balanced to get the full power out of your unit.

I wrote up a post on this a while ago, if anyone has any questions or anything they think should be added to it let me know.
Single 12V rail or multiple 12V rails? The eternal question answered


Also, you guys left the CPU off the +12 V part of your chart of what requires what voltages.
 

PreferLinux

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[citation][nom]Chesteracorgi[/nom]Very informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.[/citation]
I guess it is better to be able to use the 12 V rail as an arc welder then? Because you could if you have a >1000 W single-rail PSU. Not to mention that it won't overvolt anything – how does a high power draw cause high voltages? It generally causes low voltages. And if the PSU is a decent one, the rails will be pretty well balanced, especially for SLI or Crossfire.
 

iam2thecrowe

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[citation][nom]Chesteracorgi[/nom]Very informative and interesting. The part about single 12V vs. multiple 12V rails is important reading for system builders who opt for "safer" multiple 12V PSUs. With the current state of design of PSUs anyone planning a sli or Xfire rig is well advised to opt for the single 12V design rather than risk an imbalanced PSU that overvolts a component.[/citation]
you couldn't be more wrong.
 

Onus

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Thank you, Hunter315. Maybe that was an issue 6-8 years ago, maybe? It no longer is; I cannot imagine any possibility of creating sufficiently unbalanced +12V rail loading creating the least difficulty for any reasonable PSU.
Anyway, there were some interesting tidbits in there, like the specifics on the capacities of individual connectors. The connector type used is another area where I'd be certain the cheap PSUs skimp.
Some of it was a trip down memory lane; I remember those load resistors in the hard drive cages of the IBM PC-AT.

Edit: Oh, and your answer to the Eternal Question was very good, as was the short discussion which followed, touching on the safety issues associated with overly large +12V rails. Although I have said many of those things, I doubt I've expressed myself as clearly. Those who have read this chapter and this far into the comments would probably also like to click on your link and read that thread.
 

aidynphoenix

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It really doesn't matter weather you have a psu with a single 12v rail or several.
what matters is the quality of the power supply and how well it performs.
viewing a powesupply's voltages on a graph and seeing how far the voltages fluctuate and how smooth the ripple currents are is the most important thing.
even if your powersupply is 1200w id rather have a psu that can get the job done, but stays as close as possible to the 12v specification, and the power is clean and has little spikes.
i am a firm believer that poorly designed powersupply's is the #1 cause of premature hardisk failure aside from shipping damage and excessive heat.
you know that when company's calculate their MTBF they are useing the cleanest power possible.
I have had alot of experience with poor powersupply's and many HDD deaths.
now im running a powersupply with a very smooth 12v ripple and high tolorance (thanks corsair)
and have not had a hardisk die on me since.

i order recommend 1 seasonic, 2 corsair, 3 antec.. i do not recommend cooler-master.. or any other brand.
 

neiroatopelcc

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[citation][nom]neiroatopelcc[/nom]"Note: If you find that a system consistently fails to boot up properly the first time you turn on the switch, but that it subsequently boots up if you press the reset or Ctrl+Alt+Delete warm boot command, you likely have a problem with the Power_Good timing. You should install a new, higher-quality power supply and see whether that solves the problem." Could this explain why I only have 4-6GB memory at post, but 10GB after a quick power off and back on (didn't bother with a reset switch when designing case). Note that 10GB is still 2 short.[/citation]

To answer my own question, as nobody else probably will, I tested it. Installed a reset switch yesterday - well two wires I could shortcircuit anyway. Only effect was that my mainboard thought overclocking had failed. It didn't fix the memory issue. So this is a fat NO. PSU power good timing isn't my issue.
 
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