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quick newbie PSU question

M

MadJuggla9

2[H]4U
Joined
Oct 9, 2002
Messages
3,515
It has been a while, I am getting back into the hardware groove as i look for building my new system.

2 questions:

1. Some PSU have multiple 12v rails ..... why?
2. The 24 pin PSUs .... the extra 4 pins are for the CPU if im not mistaken? They also still have the other 4 pin connector that originated with the intels for additional power ..... Can someone explain why there are 2 instances of additional CPU power?
 
1. Because it is expensive to produce a power MOSFET that can put out 30 amps. It is much easier to have 2 15 amp MOSFETs and an effective 30 amps on two 12V rails.

2. CPUs need a lot of power, expecially Prescotts and dual core A64s.
 
MadJuggla9 said:
It has been a while, I am getting back into the hardware groove as i look for building my new system.

2 questions:

1. Some PSU have multiple 12v rails ..... why?
Click to expand...

To epand a little more on previous answer....it also isolates high draw components from one another.


2. The 24 pin PSUs .... the extra 4 pins are for the CPU if im not mistaken? They also still have the other 4 pin connector that originated with the intels for additional power ..... Can someone explain why there are 2 instances of additional CPU power?
Click to expand...

Actually the extra four just add 2 more +12v leads and 2 more grounds. They power other 12v devices on the mobo as they are from 12v1 which powers everything other than the processor which is powered off of 12v2.
 
the standalone 4-pin connector AND the additional 4 pins on the 24 pin PSU are both just extra 12v2 lines then for the cpu power?

How is it that neither are NEEDED for power, does it just overstress the other 12v lines?
 
MadJuggla9 said:
the standalone 4-pin connector AND the additional 4 pins on the 24 pin PSU are both just extra 12v2 lines then for the cpu power?

How is it that neither are NEEDED for power, does it just overstress the other 12v lines?
Click to expand...

No. The waters are getting muddy.

The 2x2 power connector, the one with two yellows (12V) and two blacks (ground) is for CPU power.

The extra 4-pins on a 24-pin connector is one 12V, one 5V, one 3.3V and one ground to provide additional power throughout the board... pretty much for everything in general.

The two 12V wires on the 24-pin cable are still on 12V1. Only the 2x2 is on 12V2.
 
jonnyGURU said:
No. The waters are getting muddy.

The 2x2 power connector, the one with two yellows (12V) and two blacks (ground) is for CPU power.

The extra 4-pins on a 24-pin connector is one 12V, one 5V, one 3.3V and one ground to provide additional power throughout the board... pretty much for everything in general.

The two 12V wires on the 24-pin cable are still on 12V1. Only the 2x2 is on 12V2.
Click to expand...

ahh perfect, thanks you guys!
 
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