I'm building a completely new PC with an RTX 5080 and an ASUS TUF Gaming 1200W power supply. The rest of the system appears to work, but connecting the monitor to the GPU produces no signal, and the motherboard shows a white GPU warning light. The BIOS also does not detect the graphics card.
I tried using the GPU's 16-pin cable, but it didn't solve the problem. The GPU also included an adapter that uses three PCIe 6+2-pin connectors. My power supply was supposed to include three compatible PCIe cables, but I can't find two of them after moving.
Could the missing adapter or PCIe cables be why the card isn't working? Would it be safe to buy another ASUS 1200W power supply of the same model and use its modular PCIe cables, or should I only use cables specifically confirmed to match this exact PSU?
3 Answers
First, check whether the power supply has a modular port intended for a 12V-2x6 or 16-pin GPU cable. If you have the correct native cable, it should be preferable to the three-connector adapter. Make sure the connector is fully seated in both the GPU and PSU, with no visible gap. You can also test a different monitor input or switch between HDMI and DisplayPort to rule out a display-cable issue.
Using cables from another modular power supply is only safe when the pinout is confirmed to be exactly the same. Matching brand and wattage is not enough, and even revisions of a model should be checked. The safest options are the original cable, a replacement cable listed specifically for that exact ASUS PSU model, or a reputable cable maker’s compatibility-verified cable. The GPU adapter can be useful for testing, but every required connector should be connected properly and ideally from separate PSU cables rather than relying on one overloaded lead.
I was considering buying another identical ASUS 1200W unit just to get its PCIe cables, but I’ll verify the exact pinout or look for a replacement cable made for this model instead.
Don’t assume the power supply is defective yet. Confirm that the card is installed directly in the primary PCIe slot rather than through a riser, and reseat it carefully. Also check that the GPU’s power connector is fully inserted. If the processor has integrated graphics, connect the monitor to the motherboard temporarily so you can enter the BIOS and verify PCIe settings. In some systems, manually trying PCIe Gen 3 or Gen 4 can help with compatibility, although the card should normally be detected automatically.
The system is completely new, and I already updated the motherboard BIOS. The BIOS still doesn’t detect the RTX 5080, so I suspect the card may not be receiving power.