I'm building a system with a Lian Li SX Platinum 1200W ATX 3.1 PSU, an ASRock X870 Creator motherboard, two AMD Radeon R9700 graphics cards, and a Ryzen 9700X. The PSU includes two 600W GPU cables: one with matching 12VHPWR-style connectors on both ends, and another with one 12VHPWR connector plus two 6+2-pin PCIe connectors.
When I connect both 6+2-pin plugs and press the power button, the PSU immediately clicks and shuts down. If I leave the small +2 sections disconnected, the system starts, but I'm unsure whether using the cable that way is safe. The same shutdown happens even with only the motherboard, CPU power, and this cable connected—without either GPU installed.
The GPUs work with the bulky 12-pin-to-3x8-pin adapter supplied with them, but I'd prefer the smaller PSU cable. Could the included cable be faulty, or am I connecting the modular cable incorrectly?
1 Answer
Double-check which end of the cable is intended for the PSU and which end is intended for the graphics card. Modular power cables are not universally wired, and a cable that physically fits can still be wrong for a particular socket. The PSU-side connectors are often solid 8-pin plugs, while the GPU-side plugs may be 6+2, so the arrangement shown sounds worth investigating carefully.
Do not run the system with only the 6-pin portions connected. The +2 sections are part of the connector and leaving them hanging can provide an incomplete or unsafe connection. Use only the exact cable supplied for this PSU, follow the PSU manual’s port diagram, and don’t force a connector into a socket. Since the PSU trips even with no GPUs attached, stop using that cable until its orientation and pinout are confirmed; if it is definitely installed correctly, the cable or PSU should be returned or tested by the manufacturer.
The fact that it shuts down with no GPU connected points away from GPU load and toward either the wrong end being plugged into the modular ports or a defective cable. Modular cables from another PSU—or a cable used backward—can cause an immediate protection trip even when the plugs fit.