Array organization and data management exploration in racetrack memory

As the descendant of
spin-transfer random access memory
(STT-RAM), racetrack memory technology saves data in magnetic domains along nanoscopic wires. Such a unique structure can achieve unprecedentedly high storage density meanwhile inheriting the promising features of STT-RAM, such as fast access speed, non-volatility, zero standby power, hardness to soft errors, and compatibility with CMOS technology. Moreover, the recent success in planar racetrack nanowire promised its fabrication feasibility and continuous scalability. In this paper, we investigate the design and optimization of racetrack memory as last-level cache by embracing design considerations across multiple abstraction layers, including the cell design, the array structure, the architecture organization, and the data management. The cross-layer optimization makes racetrack memory based last-level cache achieve 6.4
$\times$
reduction in area, 25 percent enhancement in system performance, and 62 percent saving in energy consumption, compared to STT-RAM cache design. Its benefit over SRAM technology is even more significant.