Architecting Byte-addressable Non-volatile Memories for Main Memory

Open Access
Author:
Poremba, Matthew Raymond
Graduate Program:
Computer Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 02, 2015
Committee Members:
  • John Morgan Sampson, Dissertation Advisor
  • Yuan Xie, Committee Chair
  • Vijaykrishnan Narayanan, Committee Member
  • Mary Jane Irwin, Committee Member
  • William Kenneth Jenkins, Committee Member
Keywords:
  • Computer Memory
  • Non-Volatile Memory
  • DRAM
  • Memory Scheduling
  • Memory Modeling
  • Memory Simulation
Abstract:
New breakthroughs in memory technology in recent years has lead to increased research efforts in so-called byte-addressable non-volatile memories (NVM). As a result, questions of how and where these types of NVMs can be used have been raised. Simultaneously, semiconductor scaling has lead to an increased number of CPU cores on a processor die as a way to utilize the area. This has increased the pressure on the memory system and causing growth in the amount of main memory that is available in a computer system. This growth has escalated the amount of power consumed by the system by the de facto DRAM type memory. Moreover, DRAM memories have run into physical limitations on scalability due to the nature of their operation. NVMs, on the other hand, provide high scalability well into the future and have decreased static power, one of the major sources of power consumption in contemporary systems. For all of these reasons, NVMs have the potential to be an attractive alternative or even complete replacement for DRAM as main memory. For these types of devices to be feasible, there are some obstacles that must be overcome in order for there to be a compelling reason for NVMs to augment or replace DRAM. Although the static power and scalability are better, NVMs suffers from lower performance, higher dynamic power, and lower endurance than DRAM. Furthermore, the availability of architectural and comprehensive circuit models to explore how these issues can be resolved at a high level are lacking. This dissertation addresses these issues by proposing several models for NVMs at both the architectural and circuit level. The architectural model, NVMain, is built around the assumptions that NVMs may not be complete replacements and thus provides flexibility to model complex memory systems including hybrid and distributed levels of memory. The circuit-level model, DESTINY, combines NVMs with more recent three-dimensional circuit design proposals to obtain performance and energy balanced memory designs. These two models are leveraged to explore several NVM memory designs. The first design employs a hybrid DRAM and NVM and addresses an issue of caching large amounts of NVM data in the DRAM portion. The second design considers reworking memory bank design to provide an extremely high-density NVM bank with the capability to access individual sub-units of the memory bank. The final design leverages the high parallelism from access to individual sub-units to schedule memory requests in a more efficient manner.