So lately, I had this old computer, and I wanted to add a new motherboard and gpu to it. Since I'm on a really tight budget, I'm not getting anything else more than 10$. I got the rx570 (That was almost all the money I had), which draws 150w of power max. When it came, i realized I had no 6 pin connectors to connect into the dual 6 pin to 8 pin adapter it came with. My psu is really old, and the only cables it has left are 2 molex connectors, which I'm not using. I decided to to get a dual molex to 6 pin connector, but that does not supply enough power for 150w. After some researching, I found that the MOBO PCIe slot could also provide up to 75 watts, which is more than enough. My question is that, will this work, and if it does, will the PCIe power stack with the power being supplied from the dual molex to provide at least 150 watts？I'm not an expert or have much pc building experience, so please correct me if I'm wrong.