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A survey on PCM lifetime enhancement schemes
, Article ACM Computing Surveys ; Volume 52, Issue 4 , 2019 ; 03600300 (ISSN) ; Jalili, M ; Sarbazi Azad, H ; Sharif University of Technology
Association for Computing Machinery
2019
Abstract
Phase Change Memory (PCM) is an emerging memory technology that has the capability to address the growing demand for memory capacity and bridge the gap between the main memory and the secondary storage. As a resistive memory, PCM is able to store data based on its resistance values. The wide resistance range of PCM makes it possible to store even multiple bits per cell (MLC) rather than a single bit per cell (SLC). Unfortunately, PCM cells suffer from short lifetime. That means PCM cells could tolerate a limited number of write operations, and afterward they tend to permanently stick at a constant value. Limited lifetime is an issue related to PCM memory; hence, in recent years, many studies...
A reliable 3D MLC PCM architecture with resistance drift predictor
, Article Proceedings of the International Conference on Dependable Systems and Networks ; 23- 26 June , 2014 , pp. 204-215 ; ISBN: 9781479922338 ; Arjomand, M ; Azad, H. S ; Sharif University of Technology
Abstract
In this paper, we study the problem of resistance drift in an MLC Phase Change Memory (PCM) and propose a solution to circumvent its thermally-affected accelerated rate in 3D CMPs. Our scheme is based on the observation that instead of alleviating the problem of resistance drift by using large margins or error correction codes, the PCM read circuit can be reconfigured for tolerating most of the resistance drift errors in a dynamic manner. Through detailed characterization of memory access patterns for 22 applications, we propose an efficient mechanism to facilitate such reliable read scheme via tolerating (a) early-cycle resistance drifts by using narrow margins so that considerably saving...
Exploring Emerging Memory Technologies and 3D Die-stacking for Power/Thermal-friendly Fast-memory Architectures
, M.Sc. Thesis Sharif University of Technology ; Sarbazi Azad, Hamid (Supervisor)
Abstract
As feature size of transistors in deep sub-micron technologies decreases, serious problems emerge in term of scalability, power consumption and memory access latency. A new approach to mitigate these drawbacks is to use non-volatile memory as probable alternative. Among different alternatives, Phase Change Memories (PCMs) are more likely to be used in place of conventional memories. Since fabricating PCM with 2D fashion design is a high-cost process, 3D integration is known as a good candidate solution according to its fabrication process flexibility. In 3D ICs, the increase in power density leads to elevated on-chip temperature that results in large reduction of read and write power...
A compression-based morphable PCM architecture for improving resistance drift tolerance
, Article Proceedings of the International Conference on Application-Specific Systems, Architectures and Processors ; 18-20 June , 2014 , pp. 232-239 ; ISSN: 10636862 ; ISBN: 9781479936090 ; Sarbazi-Azad, H
Abstract
Due to the growing demand for large memories, using emerging technologies such as Phase Change Memories (PCM) are inevitable. PCM with appropriate scalability, power consumption and multiple bits per cell storage capability is a probable candidate for substituting DRAM. Although storing multiple bits per cell seems to be a rational response to large memory demands, there is a significant problem to achieve this goal. Resistance drift problem is an important reliability concern that is coupled to a multi-level cell PCM (MLC PCM) memory system. In this paper, we propose a memory system architecture that, by exploiting the benefits of compression, converts resistance drift prone blocks to drift...
Addressing issues with MLC phase-change memory
, Article Advances in Computers ; Volume 118 , 2020 , Pages 111-133 ; Sarbazi Azad, H ; Sharif University of Technology
Academic Press Inc
2020
Abstract
All of the presented solutions in this book focused on using MLC phase change memory (PCM) due to density advantage and prolonging PCM lifetime. However, resistance drift can be one of the challenging issues for MLC PCMs. While it is desired to have the density advantage of MLC, the trade-off is resistance drift. Since MLCs have closely separated resistance regions, drift has a chance of overlapping intermediate regions. It may then bring out either single bit or multi-bit soft error. Indeed, drift source is related to the semi amorphous resistance regions that are metastable vs time and temperature while crystalline resistance proves to be stable across time and temperature. This chapter...
Improving Reliability and Durability of Phase Change Main Memories
,
M.Sc. Thesis
Sharif University of Technology
;
Sarbazi Azad, Hamid
(Supervisor)
Abstract
Dynamic Random Access Memory (DRAM) has been the leading main memory technology during the last four decades. In deep sub-micron regime, however, scaling DRAM comes with several challenges caused by charge leakage and imprecise charge placement. Phase Change Memory (PCM) technology is known as one of the most promising technologies to replace DRAM. Compared to competitive non-volatile memories, PCM benefits from best attributes of fast random access, negligible leakage energy, superior scalability, high density, and operating in both Single-level Cell (SLC) and Multi-level Cell (MLC) storage levels without imposing large storage overhead. Unfortunately, density advantage of MLC PCM devices...