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18A + 18A = 29A???

F

forumposter32

Gawd
Joined
Jun 19, 2005
Messages
548
Is this correct? I could swear I read my Enermax noisetaker 420 watt has dual 12V rails but has 18A on each which comes to a total of 29A. Eh, is that possible? 18 + 18 = 29?

Anyway, I'd like to know if anyone here has a link that best explains which is better between dual rails and single rails.
 
From SLCentral.com:

(14 * 12) + (16 * 12) = 336? What is this? NEW math?

You'll often find that the capabilities of the +12V rails combined almost never equal what is listed for each rail individually added together. This is because, although the two +12V rails are on separate transistors, they're still being fed by the same, single transformer and rectifier. So one rail might be able to pull off 168W if loaded up by itself, and the other might be able to pull off 192W if loaded up by itself, but the amount of juice that can even get to those transistors (safely) isn't more than 336W, so you simply CAN NOT fully load both rails to their maximum capabilities. And when I say "can not" load them, I mean load them without overloading them and staying within the tolerance of the rated rail. I mean, I put 16A loads on 14A rails all day long... that doesn't mean it's recommended. ;)
Click to expand...

http://www.slcentral.com/dual-12v-rail-psu-shootout/

So using your PSU as an example: You can put 18A on one rail, and you can put 18A on the other rail. But you can't put 18A on both rails at the same time. You can only get a total load of 29A off of both rails simultaneously. Say like 18A and 11A or 11A and 18A or 15A and 14A..... Just as long as EACH RAIL doesn't exceed 18A.
 
forumposter32 said:
How do I know how much I have on each rail?
Click to expand...

Did you just say in your original post that each rail had 18A? I'm pretty sure I read that in your post somewhere. ;)
 
forumposter32 said:
No, I mean like, how do I know I'm not USING more than 18A on either one?
Click to expand...
By calculating or measuring the max current drawn by every component connected to a single rail.

Alternatively you can keep adding components until the PSU shuts down to save itself from your actions :)
 
LOL, how do I know which devices are on which rail?
When I built my computer, I just connected things with the connectors that fit the best. I didn't notice which rail it goes to.
 
Normally, Rail 1 is for the CPU only, and Rail 2 is for everything else (which is kinda dumb, because what CPU draws 216 watts? I'd much rather have a few less Amps on Rail 1, and a few more amps on Rail 2).
 
forumposter32 said:
LOL, how do I know which devices are on which rail?
When I built my computer, I just connected things with the connectors that fit the best. I didn't notice which rail it goes to.
Click to expand...

It's listed in your Enermax's manual. Enermax actually does a good job of documenting rail loads.
 
DarkBahamut said:
Normally, Rail 1 is for the CPU only, and Rail 2 is for everything else (which is kinda dumb, because what CPU draws 216 watts? I'd much rather have a few less Amps on Rail 1, and a few more amps on Rail 2).
Click to expand...
Just give Intel time, they are bound to get there sooner or later! :(
 
DarkBahamut said:
Normally, Rail 1 is for the CPU only, and Rail 2 is for everything else (which is kinda dumb, because what CPU draws 216 watts? I'd much rather have a few less Amps on Rail 1, and a few more amps on Rail 2).
Click to expand...

Oh no! Does that mean it's going to be hard for me to upgrade to a 3400+ & Geforce 8 video card? I only have 420 watts. :eek:

Well, I thought dual rails was the standard now. Would it be easier or better to get a single rail instead?
 
forumposter32 said:
Oh no! Does that mean it's going to be hard for me to upgrade to a 3400+ & Geforce 8 video card? I only have 420 watts. :eek:

Well, I thought dual rails was the standard now. Would it be easier or better to get a single rail instead?
Click to expand...
The 3400+ is no problem & as soon as there are specs for a "Geforce 8 video card" we will see.

Dual (or more) +12V rails are the present & the future.

Dave
 
A crossload primer

in the examples its the +12V vs the +3.3\+5V
but with a dual rail +12V the maximum load on the combined +12V is limited to the listed rating and still predicated on the +3.3\+5V total wattage

its all give and take
thats why when you actually add up all the amps per rail you generally exceed the total wattage of the supply
(a 500 watt adding up to 700 watts or so )

volts x amp = wattage
 
Ice Czar said:
A crossload primer

thats why when you actually add up all the amps per rail you generally exceed the total wattage of the supply
(a 500 watt adding up to 700 watts or so )

volts x amp = wattage
Click to expand...

And that's how a Powmax can be a 580W power supply too! :D They just add up the rails instead of labeling the actual maximum capacity of any combined rails. ;)
 
jonnyGURU said:
And that's how a Powmax can be a 580W power supply too! :D They just add up the rails instead of labeling the actual maximum capacity of any combined rails. ;)
Click to expand...
I thought their marketing department determined their specs! :p
 
davidhammock200 said:
I thought their marketing department determined their specs! :p
Click to expand...
You mean as in throwing a dart at a big card filled with various ratings? I thought that that was common business practice...
 
If someone here said I could have 216 watts on one rail, does that mean I'm limited to 204 watts for anything else?
 
forumposter32 said:
If someone here said I could have 216 watts on one rail, does that mean I'm limited to 204 watts for anything else?
Click to expand...

more or less
except of course those ratings only apply at the temperature they where taken at
increase the temperature and they decrease more

few manufacturers actually test at "normal operating temperatures"
 
davidhammock200 said:
What exactly are you asking? :confused:
Click to expand...

Well, I mean that the processor would be on one rail right? And all the other devices on the other rail so wouldn't that mean if I wanted to use a very powerful video card it just would not work?
 
forumposter32 said:
Well, I mean that the processor would be on one rail right? And all the other devices on the other rail so wouldn't that mean if I wanted to use a very powerful video card it just would not work?
Click to expand...
The SLI Certified PSU's & many that are not SLI Certified, can handle 2 of the most power hungry video cards available.

This is NOT a problem. See Sticky #1 for details.
 
jonnyGURU said:
And that's how a Powmax can be a 580W power supply too! :D They just add up the rails instead of labeling the actual maximum capacity of any combined rails. ;)
Click to expand...

I replaced a PS in a 6-month old PC a while back (Barton 2600)...
Customer claimed it was unstable and had smelled like it was burning from day one.
Soon as I had the screws out I was in shock! This thing weighed less than a pound!
It was a Chiefmax "450W" supply, and I'm guessing the rating is the output it can maintain for about .02 milliseconds before exploding if you short it out. It literally weighed less than half of what a standard supply weighs, and maybe a third of what a name-brand PS weighs. Some sort of gutless (non-)wonder. Think I'd even take a Powmax over it lol.

The PC has ran fine since with a 350W Coolermaster Purepower I snagged (new) off eBay for $18 ($12 + $6 shipping).
 
Heh, a PSU isn't worth using unless its weight is sufficient to crush small pets :p
 
Ice Czar said:
catchy :p
Click to expand...
I've been sigged! :eek:

Seriously though, I've got one Power Man (Fortron/Sparkle) PSU which is rated at a mere 300/350 Watt, but is so heavy it uses an extra anchoring point at the back of the PSU with the case. The first time I removed it from the case it came in I nearly dropped it on my feet, as the sheer weight of it surprised me :D
 
Elledan said:
I've been sigged! :eek:
Click to expand...

Yeah it is kind of funny seeing something you said in soemone's sig the first time.

Someone around here has a quote of mine in there. It was something like "It is made by Young Year not Powmax(who doesn't make PSU's) but that is like saying my Gremlin pwns your Yugo".
 
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