Managing Leakage for Transient Data: Decay and Quasi-Static Memory Cells
نویسندگان
چکیده
Much of on-chip storage is devoted to transient, often short-lived, data. Despite this, virtually all on-chip array structures use sixtransistor (6T) static RAM cells that store data indefinitely. In this paper we propose the use of quasi-static four-transistor (4T) RAM cells. Quasi-static 4T cells provide both energy and area savings. These cells have no connection to Vdd thus inherently provide decay functionality: values are refreshed upon access but discharge over time without use. This makes 4T cells uniquely well-suited for predictive structures like branch predictors and BTBs where data integrity is not essential. We use quantitative evaluations (both circuit-level and cycle-level) to explore the design space and quantify the opportunities. Overall, 4T based branch predictors offers 12-33% area savings and 60-80% leakage savings with minimal performance impact. More broadly, this paper presents a different view of how to support transient data in power-aware processors.
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