There's now a standard for memory over a physical PCIe interface (https://en.wikipedia.org/wiki/Compute_Express_Link https://en.wikipedia.org/wiki/Compute_Expre

There's now a standard for memory over a physical PCIe interface (https://en.wikipedia.org/wiki/Compute_Express_Link https://en.wikipedia.org/wiki/Compute_Express_Link) and off-the-shelf products (https://www.micron.com/products/memory/cxl-memory https://www.micron.com/products/memory/cxl-memory).