# could a P/S guru explain this to me

#### N2gaming

##### Senior member

Heres where I took the data from, look under the OUTPUT section:
P/S EXAMPLE

heres the P/Ss spec info:

Output +3.3V@24A,+5V@30A,+12V1@18A,+12V2@18A,+12V3@18A, +12V4@18A,-12V@0.8A,+5VSB@3.0A

Ok, heres the video card example taken form the beloved EVGA GeForce 8800GTX :

System Requirements Minimum of a 450 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 28 Amps.)

and can be found here :

VIDEO CARD EXAMPLE

Heres my question how does the P/S put out a +12vdc @ 28amps when the specs say that the 12vdc lines are (generally around) 18/19 amps, what am I missing? thanks

#### PurdueRy

##### Lifer
Originally posted by: N2gaming

Heres where I took the data from, look under the OUTPUT section:
P/S EXAMPLE

heres the P/Ss spec info:

Output +3.3V@24A,+5V@30A,+12V1@18A,+12V2@18A,+12V3@18A, +12V4@18A,-12V@0.8A,+5VSB@3.0A

Ok, heres the video card example taken form the beloved EVGA GeForce 8800GTX :

System Requirements Minimum of a 450 Watt power supply.
(Minimum recommended power supply with +12 Volt current rating of 28 Amps.)

and can be found here :

VIDEO CARD EXAMPLE

Heres my question how does the P/S put out a +12vdc @ 28amps when the specs say that the 12vdc lines are (generally around) 18/19 amps, what am I missing? thanks

Look at the label on the side of the PSU and you will see 48A max written below all the 12V rails. These PSU's typically don't hard limit the current to just the stated amount.

However, a 8800GTX doesn't take 28A either. They are saying the entire system should have 28A of capability.

#### Zepper

##### Elite Member
Some PSUs limit their 12V rails to 20A per rail as was the intent of the split rail idea - most don't bother any more as they aren't actually split rail - often just a marketing fiction. The dummies are convinced they need split rail and they buy regardless...

.bh.

#### SerpentRoyal

##### Banned
Hehehehhh...some vendors are going back to single rail with their high-end products.

#### Modelworks

##### Lifer
One of the other things you have to watch for is that often the listed outputs are not if all outputs are loaded.

Use the simple formula Amps x Voltage = Watts.
12v x 18A = 216Watts

Now it list 4 rails.
4 x 216watts = 864Watts

That means that the 600watt supply in that link is saying it can output 864watts on the 12 volt line alone unless you read the fine print and see its saying 48A on any combination of the 12 volt lines combined .

12v x 48A = 576 watts just for the 12v line.
Your pc will need 5v and 3.3v amperage also , that would push the supply over its "600"watt rating. So it can't even deliver all the fine print voltages at the same time.