Quick PSU Question...

[fueled_by_ramen]

So I read through the PSU 101 thread and found it to be very well done and helpful. I knew some of the basics already but it clued me into some things I never considered and clarified some other things for me.

But...there is still one thing I'm fuzzy on. Let's say for example, a video card has requirements for a 350W PSU with +12 Volt current rating of 18 Amps. And a certain PSU has a +12v1 @ 16amps and a +12v2 @ 16amps...does that still mean that the PSU has a total of 16amps on the 12v rail? Or is it 32amps?

I'm confused because according to the PSU 101 info, even PSU's that say they have dual rails might in actuality have only one. So if it's +12v1 @ 16amps and a +12v2 @ 16amps, what does that mean when considering it might only be one +12v rail? Or is it still dual rails? Anyone?



On a side note...the PSU I was actually looking at comes with the Antec NSK 4400 case.
See Here
It comes with a 380W PSU. Normally I wouldn't use a PSU that comes with a case (since they are always crap) but I thought since it's Antec (which is more reputable and higher quality than most) it might be OK, at least for the time being. And since I'm not building a crazy, high-end system, I figured it should be enough juice for what I need. But, after reading some reviews on Newegg, I see some people using this case & PSU with C2D 6600's and and GeForce 8800's and so on. How the heck is this PSU powerful enough to run high-end stuff like that? Are they just nuts?

Thanks in advance.

 

[ruleworld]

But...there is still one thing I'm fuzzy on. Let's say for example, a video card has requirements for a 350W PSU with +12 Volt current rating of 18 Amps. And a certain PSU has a +12v1 @ 16amps and a +12v2 @ 16amps...does that still mean that the PSU has a total of 16amps on the 12v rail? Or is it 32amps?

its total 32 amps but 12v1 goes to cpu only. 12v2 goes to everything else including video card. so its 16 amps max available to everything else. and video card says 18amp required doesnt mean it requires 18amp for itself. my x1950 pro says 30 amps required but its peak power usage is 65 watts.

 

[fueled_by_ramen]

Thanks for clarifying it a bit more.

So let's say for the PSU in question (380W +12v1@16 and +12v2@16), the total amperage that the 12v rail can handle is 16 amps. Now, the GFX card recommends 350W PSU with +12v @18amps. I understand that the GFX card recommendation is for the total system, but it still says +12v @ 18amps. If the specs for a PSU states +12v @16amps, based on what you said that means that the +12v rail can handle 16amps maximum. Doesn't that mean that 18amps would be too high for it?

Sorry if I'm being difficult, I just want to make sure I understand this completely. PSU's were never such a big issue when I was working on PC's, but with video cards drawing more and more power now and other considerations, I need to make sure I understand it.

 

[ruleworld]

12v1 is 16A and 12v2 is 16A that wont give 32A. but will be more than 16A. he asked 16 or 32 so i said 32. didnt want to type that much. my thermaltake toughpower 750w has 4 rails each rated 18A. that should be 4x18 = 72A but it can handle 60A at most. so if u take 18A from 12v1, 12v2 and 12v3 then u will get only 6A from 12v4 even if its rated 18A.

anyway input 12v components in an online power supply calculator and find total watt for all 12v components.
http://extreme.outervision.com/psucalculator.jsp
then divide by 12 and u will get the required ampere for +12v.

 

[fueled_by_ramen]

That +12v @ 18A is total amperage across the combined +12v rails. If the PSU only has a single +12v rail at 16A then it's not enough for the system.

Right, I get that. But the PSU I was talking about is +12v1 @ 16amps and +12v2 @16amps.

And the GFX card has a requirement of +12v @ 18amps. Yes, I get that requirement is for the whole system.

So would a PSU with +12v1 @ 16amps & +12v2 @ 16amps be enough for that GFX card?

I'm confused because in PSU 101, it talks about PSU's having dual rails, but sometimes it might list two +12v rails but in actuality only have one +12v rail. If a PSU has only one listed +12v rail and it's rated at 16amps, I understand that that's less than +12v @ 18amps (simple math is no problem ) But when dual rails are included and when it might not actually even be dual rails and so on, that's when things get fuzzy.

 

[scorch]

Since I don't have enough $$$ right now for a power supply and video card I bought a 7600GS. It dosen't have any rail amp requirements it just says 300W minimum--which is what I have. I will just hold my breath and hope it works. I wish they would make it easier to determine power supply specs. Like this: this video card will require a power supply with dual rail that supports 18 amps on 12v1 and a total wattage rating of 400watts. There are also people that mix in watts into the mix to determine amps. I can do math but, Multiply this divide this by 12.... What the heck. Im not a noob but reasearching a damn power supply geez.

 

[ruleworld]

volt x ampere = watt. so calculate total wattage of all your 12v devices like gfx card, cpu, mobo, hd, dvd drive, sound card, fan etc. then u get the total watt required at 12v rail. divide by 12 u get the ampere on 12v rail.

ampere = watt / volt

in this case

12v rail ampere = total 12v watt / 12