Power Supply Amperage

[MotF Bane]

What is the significance of amperage for a power supply?

 

[Puffnstuff]

Well if you think of amperage like fishing line then would you go deep sea fishing with an ultralight rig and 5lb test line? No you wouldn't. You have to look at the amperage on all of the rails and make sure that it has enough to meet the demands of your system plus anything that you might want to add in the future. The 12v rail is the most heavily taxed on a modern system so low amperage on it could cause many problems. I'm a firm believer in redundancy and operating headroom which is why I run the ps that I do. No it isn't cheap however I don't have to worry about power problems today or tomorrow when I add more stuff to it. I personally wouldn't recommend any ps that didn't have at least 18a or better on each 12v rail or 36a or better on a single 12v rail. My kids are running enermax liberty 620's which have 22a x 2 on the 12v rails.

 

[jonnyGURU]

What? The thread you started over at XtremeSystems wasn't good enough?

Watts is Amps multiplied by Volts. The wattage you see on a label as part of the model name, etc. is only the sum of all of the rails combined. Since your power supply supplies different voltages on different "rails", that total power output really doesn't mean much when doing side by side comparisons.

For example: 5V @ 40A is 200W. And 12V @ 17A is 200W. Which is more important? Well... considering that your CPU gets it's juice from a regulated +12V lead (either a 4-pin or 8-pin power connector) and your video cards regulate the GPU's core voltage off of the +12V rail (either from a PCI-e connector or through the slot) I'd say the +12V rail. Then of course you have fans, drive motors, Firewire... all use +12V.

+5V isn't used much anymore, but it's still important. Some boards regulate RAM voltage from the +5V (most still use +3.3V.) The logic boards of all of your drives use +5V and PCI cards used +5V. USB uses +5V. But the loads of all of those devices together don't even come close to the load put on a +12V rail. So if looking at two power supplies of equal build quality and price and the both have the same "total output wattage" claim and one has more amperage available on the +12V rail than the other, I'm going to pick the one with more amperage on the +12V rail.

 

[MotF Bane]

Sorry Jonny. I went over here too, just to get an amperage explanation, because XS can be a little hard to follow sometimes for me
Thanks for posting twice now lol.