Hi. My current power supply bought in late 2011 has 6 12v rails. I've noticed most advertised have only a single 12v rail. just wondering what are the differences? (longevity? cleaner power? etc). although ill probably see a lot more use out of my current setup before upgrading but was just curious. is it just marketing hype?
http://www.overclock.net/t/761202/single-rail-vs-multi-rail-explained
I can't explain it well, but the author of that thread can.
Convenience is the difference - with a single 12V rail, you don't have to worry about load balancing and falling short on amperage. If you use a multi-rail design, and say you're trying to power a GPU that needs more amperage than one of your 12V rails can deliver, you have to make sure you plug in PCI-e power connectors from separate 12V rails. With a single 12v rail PSU, as long your PSU has enough recommended wattage, the single 12v rail will usually enough amperage (wattage = voltage (12v, in the case of rails and main components) * amperage). Also, PSU's with a single 12v rail tend to have higher build quality, but there are good multi-rail designs out there.
Multi-rails do have advantages as well - first of all, redundancy: if you're unfortunate enough to have a dead 12v rail, the PSU could still function until you find a replacement. Second is because the amperage is spread out, if the worst to happen (an explosion), the affects of said catastrophe would be greatly reduced due to relative low amperage compared to a single 12v rail design.
I, personally, prefer having a single 12V rail, but my current 750w PSU has 4x 12v rails and has no problem powering a 4.5GHZ Core i5 2500k and a 1202MHz GTX 760.
love your responses. read the article too wiemerimer. I think I personally prefer the multi rail system having got this new info. massive current is great but I'd side more with the redundancy argument. Thank you so much. I am satisfied being that little bit wiser.