  3D die stacking has often been proposed to build large-scale DRAM-based
caches. Unfortunately, the power and performance overheads of DRAM limit the
efficiency of high-bandwidth memories. Also, DRAM is facing serious scalability
challenges that make alternative technologies more appealing. This paper
examines Monarch, a resistive 3D stacked memory based on a novel reconfigurable
crosspoint array called XAM. The XAM array is capable of switching between
random access and content-addressable modes, which enables Monarch (i) to
better utilize the in-package bandwidth and (ii) to satisfy both the random
access memory and associative search requirements of various applications.
Moreover, the Monarch controller ensures a given target lifetime for the
resistive stack. Our simulation results on a set of parallel memory-intensive
applications indicate that Monarch outperforms an ideal DRAM caching by 1.21x
on average. For in-memory hash table and string matching workloads, Monarch
improves performance up to 12x over the conventional high bandwidth memories.
