Coordinated refresh: Energy efficient techniques for DRAM refresh scheduling

As the size and speed of DRAM devices increase, the performance and energy overheads due to refresh become more significant. To reduce refresh penalty we propose techniques referred collectively as "Coordinated Refresh", in which scheduling of low power modes and refresh commands are coordinated so that most of the required refreshes are issued when the DRAM device is in the deepest low power Self Refresh (SR) mode. Our approach saves DRAM background power because the peripheral circuitry and clocks are turned off in the SR mode. Our proposed solutions improve DRAM energy efficiency by 10% as compared to baseline, averaged across all the SPEC CPU 2006 benchmarks.