https://wccftech.com/amd-radeon-rx-5600-xt-rx-5700-dx12-multi-gpu-tests-up-to-71-percent-faster/

Multi-GPU support was a fascinating technology back when it launched, allowing users to pair up two or more graphics cards for higher performance rather than purchasing a single and costlier graphics card. However, a decade has gone by and there has been no significant progress in the multi-GPU field with many vendors, AMD & NVIDIA, dropping support for it entirely due to poor scaling across multiple cards, non-optimization in applications and various other issues. But this doesn't mean that users who want to try out multi-GPU cannot do so anymore, and that's what the folks over at Uniko's Hardware have just done so, pairing up a Radeon RX 5700 graphics card with a Radeon RX 5600 XT to see how they perform.

As stated, AMD and NVIDIA have almost entirely dropped support for Multi-GPU on their current generation of graphics cards. AMD's Crossfire is no more but that has been replaced by XDMA, a protocol that links GPUs over the PCIe interface. NVIDIA, on the other hand, allows multi-GPU only on its high-end graphics cards through the NVLINK interconnect with the SLI days far gone. While AMD's XDMA link doesn't allow you to mix and match two separate graphics cards, with DirectX 12's and Vulkan API's mGPU explicit adapter, you can combine two different GPUs with different configurations.