Evaluation of Core Hopping on POWER7
Shinobu Miwa, Charles R. Lefurgy · ACM SIGMETRICS Performance Evaluation Review · 2014
Controlling and limiting the peak runtime temperature of a microprocessor has the potential to reduce chip leakage power consumption, improve chip reliability, reduce provisioned cooling, and reduce operational costs. Previously, the technique of core hopping has been proposed as one method to reduce peak runtime temperature. However, there is no study that shows core hopping is beneficial for modern many-core microprocessors found in high-end servers. This paper thoroughly examines heat spreading in the 8-core POWER7 microprocessor which provides 5 temperature sensors per core. We find that the POWER7 heatsink has excellent heat spreading capabilities which negates the benefits of core hopping. We conclude that high-performance servers with similar thermal solutions will also not see benefit from core-hopping methods.