A New Limited Directory

The cache coherence scheme for a scalable distributed shared memory multiproces-sor should be eecient in terms of memory overhead for maintaining the directories, as well as network latency for a memory request. In this paper, we propose a cache coherence scheme which minimizes the memory access delay and at the same time, reduces the directory overhead by using a limited directory scheme. In the proposed scheme, pointer overrow is handled by using a logically embedded ring for transmitting control messages. Wormhole routing, in conjunction with the usage of ring, introduces a snoopy behavior into the proposed scheme. We will show, with the help of several execution driven simulation results, that for real applications our technique outperforms the full map directory scheme, as well as the traditional implementations of limited directory schemes.