Need PSU Information dump

EDIT. I see you got a good link. More info on it for sure

Computer power supplies convert your household power from 120/240 volts AC to 12/5/3.3/-15/-5 volts DC.

Now this can be done more than one way.

Computers use a switching system(high efficiency and lighter than a linear system that may be found in old power amps).

Older units had the hardware to make each voltage rail separately(for the most part). at the time the lower rails 3.3 and 5 volts got more use out of them and they had more of the overall power on these rails.

As cpu power requirements grew and supply voltages dropped more and more parts started being run from the 12 volt rail(and then regulated down to the needed voltage). This is why OLDER power supplies are not suitable for modern systems. that make heavy use of the 12 volt rail and less use of the lower rails.

Newer power supplies started a new trick. HUGE 12 volt rails and then using regulators(dc-dc converters) to get the 5 and 3.3 volt rails. This allows the newer power supplies to still have a fair bit of 5 and 3.3 volt power and massive amounts of the now in high demand 12 volt power.

In this new system, If a system is not pushing high loads on the lower rails, the 12 volt rail has MUCH more power than the older ones. This works out well for modern 12 volt heavy systems.

At some point the ATX spec(they must have dropped this later) called for multi rail power supplies. almost all of the multi rail power supplies simply contain a current limiter to prevent users from overloading a single wire(too many Y adapters connected to all kinds of hardware).


In most cases either power supply type works out fine.

While you will see many pro/cons to each style. The truth is it will be RARE that either will cause an issue.

You can load up a single rail and try to run 3 video cards(with 2 6 pin cables each) off of 1 pci-e cable with splitters. This would lead to excess current flow in the wire and heat or damage to the wire.

You will see users who say power is wasted on an un-used rail, but on most power supplies the total of the rails is greater than the main rail(combined 12 volt current/wattage/amperage) that feeds them all meaning you can not pull max out of all rails anyway. Some power supplies DO work this way(adding the rails is the same as combined. more often than not it does not work this way), but I have never seen it cause a real world issue

As you can see here the COMBINED 12 volt current is 22amps MAX while if one was to try to ADD the rails they would get 30 amps(360 watts out of a 300 watt power supply is not going to happen).


Now you also have to watch out for cheap power supplies as they cut corners by removing protections(over current/voltage ect) OR using very old designs that while they worked back in the day are NOT suitable for modern systems.

These old designs are also easy to make VERY high wattage units with 5/3.3 volt and low 12 volt ratings. So on paper it IS a 550 watt power supply(looks good for 20$ no?), but only 200 watts of it is on the 12 volt rail causing it to fail under load. The lack of protection may cause it to fry your system when it does.

A quality unit will SHUT DOWN under any condition that can damage the power supply or system it is connected to.

I hope this gives you a quick bit of PSU info.