I got an RTX 3070 for free and tried installing it in my older PC, but I only get a black screen. The card's fans and lights turn on, yet there is no display. My system has a Ryzen 1800X, 16 GB of Corsair Vengeance DDR4-3200 running at 3000 MHz, a B350 motherboard, and previously used a GTX 1070 without problems. I updated the motherboard BIOS to the latest version, and the PC still works normally with the GTX 1070. The 3070 worked the last time it was installed, but that original computer's motherboard later failed, so I cannot currently test the card there. The power supply is rated at 650 W. What troubleshooting steps should I try?
3 Answers
A 650 W power supply is generally around the recommended range for an RTX 3070, but the exact model and its condition matter. Make sure you are using the proper PCIe power connectors directly from the PSU rather than loose or questionable adapters, and confirm the cables are fully seated.
It is also worth considering that the 3070 itself may have developed a fault. Since the previous system it was in had a failed motherboard, you cannot assume the card is still healthy. Testing it in another known-working PC, or having a repair shop test it, would help separate a compatibility problem from a defective GPU.
First, double-check the CPU model—it sounds like a Ryzen 7 1800X, since there was no 1800X3D. You may want to check that the BIOS version still supports the 1800X, although the fact that the system boots with the GTX 1070 suggests the update is okay. In the BIOS, try disabling CSM, connect the monitor to different outputs on the 3070, and verify that all required PCIe power cables are firmly connected. You could also install the 3070 in a secondary PCIe slot while booting with the 1070, then check whether Windows detects it.

It is an 1800X—my mistake. The BIOS update didn’t cause any obvious issues because the PC still runs normally with the 1070. I’ll try those other suggestions.