Only attach the GT540 to the monitor, and check you have the latest drivers for it. Hopefully this will at least stop it seeing the other chip.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
