Dr. Eric Rotenberg, ECE Department
Dr. Eric Rotenberg has been awarded $40,000 by the NCSU Center for Advanced Computing & Communication towards research on Retention-Aware Placement in DRAM (RAPID): Software Methods for Quasi-Non-Volatile DRAM.
The award will run from July 1st, 2007 to June 30th, 2008.
Research Abstract - DRAM is predicted to displace SRAM in future embedded systems (cell phones, sensor nodes, etc.) as functionality evolves. This future can be better met by dealing with the DRAM refresh problem and thereby reap the capacity benefits of DRAM without impacting battery life.
The key lies with exploiting dramatic variations in retention times among different DRAM pages. We recently proposed Retention-Aware Placement in DRAM (RAPID), novel software approaches that can exploit off-the-shelf DRAMs to reduce refresh power to vanishingly small levels approaching non-volatile memory. The key idea is to favor longer-retention pages over shorter-retention pages when allocating DRAM pages. This allows selecting a single refresh period that depends on the shortest-retention page among populated pages, instead of the shortest-retention page overall. We explore three versions of RAPID and observe refresh energy savings of 83%, 93%, and 95%, relative to conventional temperature-compensated refresh. RAPID with off-the-shelf DRAM also approaches the energy levels of idealized techniques that require custom DRAM support. This ultimately yields a software implementation of quasi-non-volatile DRAM.
In addition to providing real value for highly-functional, energy-constrained, and cost-constrained computing/communication devices, we believe RAPID is inexpensively deployable because it is based solely on software and commodity off-the-shelf DRAM. The next step in this research is to integrate RAPID into one or more real system prototypes of interest to CACC members, including a cell phone and/or a sensor node.