Portable systems demand energy eflciency in order to maximize battery l&e. IRAM architectures, which combine DRAM anda processor on the same chip in a DRAMprocess, are more energy e$cient than conventional systems, The high density of DRAMpermits a much larger amount of memory on-chip than a traditional
SRAM cache design in a logic process. This allows most or all IRAMmemory accesses to be satisfied on-chip. Thus there is much less need to drive high-capacitance off-chip buses, which contribute significantly to the energy consumption ofa system. To quanhfy this advantage we apply models of energy consumption in DRAM and SRAMmemories to results from cache simulations of applications reflective of personal productivity tasks on low power systems. We find that #AMmemory hierarchies consume as little as 22% of the energy consumed by a conventional memory hierarchy for memoryintensive applications, while delivering comparable perJormance. Furthermore, the energy consumed by a system consisting of an IRAM memory hierarchy combined with an energy eficient CPU core is as little as 40% of that of the same CPU core with a traditional memory hierarchy.