What is CXL, and why should you care?

If you purchase a server in the next few months featuring Intel’s Sapphire Rapids generation of Xeon Scalable processor or AMD’s Genoa generation of Epyc processors, they will come with a notable new function called Compute Express Link (CXL)—an open interconnect standard you may find useful, especially in future iterations. CXL is supported by pretty much every hardware vendor and built on top of PCI Express for coherent memory access between a CPU and a device, such as a hardware accelerator, or a CPU and memory. PCIe is meant for point-to-point communications such as SSD to memory, but CXL will eventually support one-to-many communication by transmitting over coherent protocols. So far, CXL is capable of simple point-to-point communication only.