the s3 is just at the edge of 200w per board, if you have a psu with 2 ends per cord, it will be overloaded.
its important to use a PSU that has 4 separate cables per s3.
ur right.
since my psu only have 2 pci-e, i change cpu connector (8 pin 12V) into pci-e.
its not easy to take pins out from connector, do it carefully.
there is another 12V pin at the atx connector, but its too complicated because the cable tied up as one.
drawback for this methode is unable to use psu for cpu directly.you have to reverse it before plug it to cpu.
simple way is use 4 cable psu(not 2 cable 4 connector).
S3+ as long as you are not overclocking a lot 2 cables should power it. One pcie power cable to each side.
S5 is a different story 4 power cables is needed. But it uses more watts.
A big thing is either one dont use a cheap PSU. If you use a cheap psu it's cords are probley not enough guage and it will get hot.
that because i use "cheap" psu. it comes with 2 cable but 4 connector pcie(2x2 parallel)
first attempt cable get hot, after modification slightly warm.
sure cable gauge is the problem, psu component itself can handle the wattage(mine 650).
from april till now 3+ months work fine with 0 problem.
edit:not overclock. had oc before but it burned my psu(same psu with the last one).