15th IEEE International Conference on Application-Specific Systems, Architectures and Processors (ASAP'04)
Register Organization for Enhanced On-Chip Parallelism
Galveston, Texas
September 27-September 29
ISBN: 0-7695-2226-2
Large register file with multiple ports is a critical component of a high-performance processor. A large number of registers are necessary for processing a larger number of in-flight instructions to exploit higher instruction level parallelism (ILP). Multiple ports for a register file are necessary to support execution of multiple instructions each cycle. These necessities lead to a larger register access time. However, register access time has to be minimal to enable design of high frequency processors. Analysis of lifetime of a logical to physical register mapping reveals that there are long latencies between the times a physical register is allocated, consumed, and released. In this paper, we propose a dual bank register file organization that exploits such long latencies, resulting in a large bandwidth with a reduced register access time. Implementation of one flavor of the proposed register file organization, as compared to a conventional monolithic register file, in an 8-wide out-of-order issue superscalar processor enhanced instructions per cycle (IPC) throughput up to 6% for Spec2000 applications while reducing register access time up to 22%. Another flavor of the register file organization, with a similar access time as the conventional monolithic register file, enhanced the IPC up to 15%. Thus a trade-off between register access time and ILP exploitation is shown.
Citation:
Rama Sangireddy, "Register Organization for Enhanced On-Chip Parallelism," asap, pp.180-190, 15th IEEE International Conference on Application-Specific Systems, Architectures and Processors (ASAP'04), 2004