CCIX (the “cache-coherent interconnect for accelerators,” pronounced “see-six”), is a new, high-speed, chip-to-chip I/O protocol being developed by the CCIX Consortium. It’s based on the ubiquitous PCIe protocol, which means it can leverage PCIe’s existing, low-cost hardware infrastructure but it can go faster—a lot faster. While PCIe 4.0 (just starting to roll out) operates at a maximum rate of 16GTransfers/sec—that’s about 64Gbytes/sec bidirectionally on a 16-lane link—CCIX takes the signaling to 25GTransfer/sec, which approaches 100Gbytes/sec bidirectionally over the same 16 lanes. For compatibility, CCIX connections initialize as PCIe connections, thus maintaining PCIe protocol compatibility, but then permit a bootstrap mechanism where two connected CCIX devices can agree to stomp on the I/O accelerator pedal for a 56% speed boost using the same hardware.
All of this and more is explained in a new, easy-to-read technical bulletin posted by Synopsys titled “An Introduction to CCIX.”
Synopsys is a CCIX Contributor and Xilinx is a CCIX Promoter—both members of the CCIX Consortium at different membership levels. Xilinx is intensely interested in I/O protocols like CCIX to permit ever-faster communications between fast processor arrays and even faster FPGA-based accelerators and is looking forward to the first products with CCIX interconnect sampling later this year.