A network on chip (‘NOC’) that includes integrated processor (‘IP’) blocks, routers, memory communications controllers, and network interface controllers; each IP block adapted to a router through a memory communications controller and a network interface controller; and at least one IP block also including a computer processor and an L1, write-through data cache comprising high speed local memory on the IP block, the cache controlled by a cache controller having a cache line replacement policy, the cache controller configured to lock segments of the cache, the computer processor configured to store thread-private data in main memory off the IP block, the computer processor further configured to store thread-private data on a segment of the L1 data cache, the segment locked against replacement upon cache misses under the cache controller's replacement policy, the segment further locked against write-through to main memory.