  In recent years, the size and leakage energy consumption of large last level
caches (LLCs) has increased. To address this, embedded DRAM (eDRAM) caches have
been considered which have lower leakage energy consumption; however eDRAM
caches consume a significant amount of energy in the form of refresh energy. In
this paper, we present a technique for saving both leakage and refresh energy
in eDRAM caches. We use dynamic cache reconfiguration approach to intelligently
turn-off part of the cache to save leakage energy and refresh only valid data
of the active (i.e. not turned-off) cache to save refresh energy. We evaluate
our technique using an x86-64 simulator and SPEC2006 benchmarks and compare it
with a recently proposed technique for saving refresh energy, named Refrint.
The experiments have shown that our technique provides better performance and
energy efficiency than Refrint. Using our technique, for a 2MB LLC and 40
micro-seconds eDRAM refresh period, the average saving in energy over eDRAM
baseline (which periodically refreshes all cache lines) is 22.8%.
