Mentioned in the latest Linux patches, AMD XGMI interconnect is rumored to offer bandwidths of up to 64 GB/s on the current PCIe 3.0 standard, possibly even higher on the upcoming PCIe 4.0. This should compete with Nvidia's NVLink, which currently offers bandwidths of up to 200 GB/s on PCIe 3.0 and could exceed 300 GB/s next year with the jump to the PCIe 4.0 standard.
https://www.notebookcheck.net/AMD-Radeon-Vega-20-GPUs-will-get-XGMI-PCIe-4-0-to-compete-with-Nvidia-s-NVLink.329034.0.html