As I understand it, NVLink isn't actually required for much of anything. It allows P2P transfers and atomics. That same functionality can be used over PCIe on s

As I understand it, NVLink isn't actually required for much of anything. It allows P2P transfers and atomics. That same functionality can be used over PCIe on some GPUs with reduced performance. And the P2P features are not transparent and are lower-performance than staying inside one GPU, so generally software avoids P2P transfers even when they are available. The Nvidia documentation on this is absolutely horrible, the features vary wildly by model of GPU, and I claim no real expertise.