Re: Upgrade Graphics card
the 4 pin molex runs on the 5v rail, whereas the 6pin and 8pin run off of the 12v rail. The 5v rails are less powerful and generally has less power allocated to it, power is split up between the 3v, 5v and 12v, and are generally used for your optical drives, hard drives, fan controllers and fans, and the 12v is for your motherboard/cpu and gpu.
To know for sure what you'll need we'll need to know exactly what your PSU has for connections, easiest way would be to just give us a link of the PSU or pop open your case and rattle off what's there for cables.
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