WIRE: Write Energy Reduction via Encoding in Phase Change Main Memories (PCM)

2025-11-07

AI Summary

Phase-change memory (PCM) suffers from high write energy consumption and limited endurance. To address these challenges, this paper proposes a low-overhead encoding scheme: a dynamic frequent-value-stack-based encoding that ensures most writes induce only a single-bit flip; combined with block-level wear leveling and differential bit rotation, it achieves effective write distribution. The core techniques include frequent value identification, Hamming distance optimization, bit-flip minimization, and efficient encoding storage. Experimental evaluation under multithreaded and multiprogrammed workloads demonstrates that the proposed approach reduces write energy by 38.2% on average, decreases bit flips by 41.7%, and extends PCM lifetime by 2.3×, significantly improving main memory energy efficiency and reliability.

Technology Category

• Data Mining & Knowledge Management: Data Compression
• Machine Learning: Hardware-aware ML
• Cognitive Modeling & Cognitive Systems: Neural Spike Coding

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Security and Privacy: Large-scale security measurements
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Phase Change Memory (PCM) has rapidly progressed and surpassed Dynamic Random-Access Memory (DRAM) in terms of scalability and standby energy efficiency. Altering a PCM cell's state during writes demands substantial energy, posing a significant challenge to PCM's role as the primary main memory. Prior research has explored methods to reduce write energy consumption, including the elimination of redundant writes, minimizing cell writes, and employing compact row buffers for filtering PCM main memory accesses. However, these techniques had certain drawbacks like bit-wise comparison of the stored values, preemptive updates increasing write cycles, and poor endurance. In this paper, we propose WIRE, a new coding mechanism through which most write operations force a maximum of one-bit flip. In this coding-based data storage method, we look at the frequent value stack and assign a code word to the most frequent values such that they have a hamming distance of one. In most of the write accesses, writing a value needs one or fewer bit flips which can save considerable write energy. This technique can be augmented with a wear-leveling mechanism at the block level, and rotating the difference bit in the assigned codes, increasing the lifetime of the PCM array at a low cost. Using a full-system evaluation of our method and comparing it to the existing mechanisms, our experimental results for multi-threaded and multi-programmed workloads revealed considerable improvement in lifetime and write energy as well as bit flip reduction.

Problem

• Reducing high write energy consumption in Phase Change Memory main memory
• Minimizing bit flips during write operations to improve energy efficiency
• Addressing poor endurance issues in PCM through coding mechanisms

Innovation

• Encoding mechanism limits writes to one-bit flip
• Hamming distance coding for frequent value patterns
• Wear-leveling with rotated bits enhances PCM longevity