12v rail problem?

[peasantdestroya69]

My friend says that his psu is only outputting 5v and 3.3v to the 24pin connector. Does this imply a bad psu?

 

[Dark Lord of Tech]

That doesn't make sense here's the rail ranges.

 

[nukemaster]

My friend says that his psu is only outputting 5v and 3.3v to the 24pin connector. Does this imply a bad psu?

How are they seeing that it is only putting out 5 and 3.3? I mean you can not even boot a computer without 12 since the cpu regulators are powered from the 12 volt rail as are many other parts of the system(hard drive motors/fans/video cards/ect).

 

[skit75]

Could be an older system. Migration to +12VDC "carrying the load" has only been around about ten years. Before that, the +3.3V and +5V rails did all the heavy lifting and +12V was only used for HDD\Optical Drives.

 

[nukemaster]

Could be an older system. Migration to +12VDC "carrying the load" has only been around about ten years. Before that, the +3.3V and +5V rails did all the heavy lifting and +12V was only used for HDD\Optical Drives.

This is true. As power requirements grew the wire gauge would have had to increase quite a bit so 12 volts was the only option.

150 watts @ 12 volts is 12.5 amps
150 watts @ 5 volts is 30 amps
150 watts @ 3.3 volts is 45.45 amps
Higher current needs larger wire.