A system and method are provided for increasing the number of processors on a single integrated circuit to a number that is larger than would typically be possible to coordinate on a single bus. In an embodiment of the present invention a two-level memory coherency scheme is implemented for use by multiple processors operably coupled to multiple buses in the same integrated circuit. A control device, such as node controller, is used to control traffic between the two coherency levels. In an embodiment of the invention the first level of coherency is implemented using a "snoopy" protocol and the second level of coherency is a directory-based coherency scheme.