Originally posted by: 4fingerwu1
What exactly does a rail refer to ?
Is it the acuall wire that is comes out of the power supply so for example does a power supply with 4 12v rails have 4 different wires extending from it ?
It means groups of wires.
E.g. if you have a dual-rail 12 V PSU, with 5 wires coming out - 3 might be from 1 rail and 2 from the other.
The individual 'rails' have independent overload protection (if you overload any one of them, the PSU should shutdown). They may, or may not, be independently voltage regulated.
The idea of having multiple 'rails' is a safety feature required by "underwriters' laboratories" who set basic safety standards for insurance purposes. Essentially, manufacturer's aren't supposed to leave exposed 12 V wires with more than 20A available where they can easily be touched by the user. At that sort of voltage and current, things could easily catch fire before the PSU shuts down.
Anyway, a 1950XT doesn't need anywhere near 30A. 15A is more like it. Even an entire system with a 1950 doesn't need 30 A.
However, by making absurdly high recommendations, ATI avoid people buying inferior PSUs which may not stand up to the load required (especially, if the PSU is badly installed, and poorly ventilated).
Facebook
Twitter