You need both molex and 6 or 8 pin PCI-E on the cards.
If you don't plug in one of them the card won't work.
The molex can give up to 60-75 watts to the card (limitation of PCI-E), the 6-pin PCI-E can do another 75W and 8-pins can do 150W.
You basically have 3 options:
- get a better PSU;
- add a secondary PSU (can be tricky);
- split the 6 or 8 pin cables (NOT recommended, even if the PSU could handle it);
Whatever you do, always use powered risers.
I need to do this second tricky part you said
Because more than 1000w psu here in my country cost alot of money , i though about adding second psu i have a good electrical knowledge , put just afraid anything goes out of control can you share any details incase you have done this before , how to make the grounds common i know the separate psus will have isolated grounds , also the power on/off signal i can make a circuit to do this trick or just jumper the addition psu as i don't turn off my miners . any experience to share?? ..thx
I always avoided using dual PSUs. It just always felt fishy to me. And I always avoided cheap PSUs (using mostly EVGA Supernova G2 1300W PSUs which come with 10 years of warranty) because poor quality PSU can do some real damage and because electricity fluctuates a lot down (-5-20%) where I live. So I don't have any experience with dual PSUs but there are a lot of guides and debates how it should be done properly.
Another option would be to get an old server PSU, those are very cheap even the big ones (1-2kW) and they're designed to run 0-24 but you would need to solder some extra wires on them.