SGI continued to enhance its line of servers (including some supercomputers) based on the SN architecture. SN, for Scalable Node, is a technology developed by SGI in the mid-1990s that uses cache-coherent non-uniform memory access (cc-NUMA). In an SN system, processors, memory, and a bus- and memory-controller are coupled together into an entity called a node, usually on a single circuit board. Nodes are connected by a high-speed interconnect called NUMAlink (originally marketed as CrayLink). There is no internal bus, and instead access between processors, memory, and I/O devices is done through a switched fabric of links and routers.