Sharif Digital Repository

Non-volatile memory (NVM) technologies are promising alternatives to traditional CMOS memory technologies. While NVMs were primarily studied to be used in the memory hierarchy, they can also provide benefits in reconfigurable systems such as Field-Programmable Gate Arrays (FPGAs). In this paper, we investigate the applicability of different NVM technologies for the configuration bits of FPGAs and propose a power-efficient reconfigurable architecture based on Phase Change Memory (PCM). Quantitative analysis for various FPGA architectures using different memory technologies shows the benefits of the proposed scheme  

Graphics Processing Units (GPUs) employ large register files to accommodate all active threads and accelerate context switching. Unfortunately, register files are a scalability bottleneck for future GPUs due to long access latency, high power consumption, and large silicon area provisioning. Prior work proposes hierarchical register file, to reduce the register file power consumption by caching registers in a smaller register file cache. Unfortunately, this approach does not improve register access latency due to the low hit rate in the register file cache. In this paper, we propose the Latency-Tolerant Register File (LTRF) architecture to achieve low latency in a two-level hierarchical... 

Graphics Processing Units (GPUs) employ large register files to accommodate all active threads and accelerate context switching. Unfortunately, register files are a scalability bottleneck for future GPUs due to long access latency, high power consumption, and large silicon area provisioning. Prior work proposes hierarchical register file to reduce the register file power consumption by caching registers in a smaller register file cache. Unfortunately, this approach does not improve register access latency due to the low hit rate in the register file cache. In this article, we propose the Latency-Tolerant Register File (LTRF) architecture to achieve low latency in a two-level hierarchical... 

Emerging nonvolatile memory technologies, such as spin-transfer torque RAM or resistive RAM, can increase the capacity of the last-level cache (LLC) in a latency and power-efficient manner. These technologies endure 109 - 1012 writes per cell, making a nonvolatile cache (NV-cache) with a lifetime of dozens of years under ideal working conditions. However, nonuniformity in writes to different cache lines considerably reduces the NV-cache lifetime to a few months. Writes to cache lines can be made uniformly by wear-leveling. A suitable wear-leveling for NV-cache should not incur high storage and performance overheads. We propose a novel, simple, and effective wear-leveling technique with... 

With the recent development in Non-Volatile Memory (NVM) technologies, several studies have suggested using them as an alternative to SRAMs in on-chip caches. However, limited endurance of NVMs is a major challenge when employed in the caches. This paper proposes a data manipulation technique, so-called Wearout Informed Pattern Elimination (WIPE), to improve the endurance of NVM-based caches by reducing the activity of frequent data patterns. Simulation results show that WIPE improves the endurance by up to 93% with negligible overheads. © 2017 IEEE  

With the development of Non-Volatile Memory (NVM) technologies in recent years, several studies suggest using them as an alternative for SRAMs in on-chip caches. One of the main challenges in replacing SRAMs with NVMs is limited endurance of NVMs (i.e. the maximum allowed number of write operations in an NVM cell). The endurance of NVM caches is directly affected not only by workload behaviors, but also by process variations (PVs). Several studies characterized the endurance of NVM caches but they do not consider the simultaneous effects of the PVs and the workloads. In this paper, we propose a high-level framework to investigate the endurance of NVM caches affected by the per-cell endurance... 

Recent development in memory technologies has introduced Spin-Transfer Torque Magnetic RAM (STT-MRAM) as the most promising replacement for SRAMs in on-chip cache memories. Besides its lower leakage power, higher density, immunity to radiation-induced particles, and non-volatility, an unintentional bit flip during read operation, referred to as read disturbance error, is a severe reliability challenge in STT-MRAM caches. One major source of read disturbance error in STT-MRAM caches is simultaneous accesses to all tags for parallel comparison operation in a cache set, which has not been addressed in previous work. This paper first demonstrates that high read accesses to tag arrays extremely... 

Checkpointing with rollback recovery is a well-established technique to tolerate transient faults. However, it incurs significant time and energy overheads, which go wasted in fault-free execution states and may not even be feasible in hard real-time systems. This paper presents a low-overhead two-state checkpointing (TsCp) scheme for fault-tolerant hard real-time systems. It differentiates between the fault-free and faulty execution states and leverages two types of checkpoint intervals for these two different states. The first type is nonuniform intervals that are used while no fault has occurred. These intervals are determined based on postponing checkpoint insertions in fault-free... 

As technology process node scales down, on-chip SRAM caches lose their efficiency because of their low scalability, high leakage power, and increasing rate of soft errors. Among emerging memory technologies, Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM-based cache memories. The main advantages of STT-MRAM are its non-volatility, near-zero leakage power, higher density, soft-error immunity, and higher scalability. Despite these advantages, high error rate in STT-MRAM cells due to retention failure, write failure, and read disturbance threatens the reliability of cache memories built upon STT-MRAM technology. The error rate is significantly... 

As technology process node scales down, on-chip SRAM caches lose their efficiency because of their low scalability, high leakage power, and increasing rate of soft errors. Among emerging memory technologies, Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM-based cache memories. The main advantages of STT-MRAM are its non-volatility, near-zero leakage power, higher density, soft-error immunity, and higher scalability. Despite these advantages, high error rate in STT-MRAM cells due to retention failure, write failure, and read disturbance threatens the reliability of cache memories built upon STT-MRAM technology. The error rate is significantly... 

Non-Volatile Memory (NVM) technology is a promising solution to fulfill the ever-growing need for higher capacity in the main memory of modern systems. Despite having many great features, however, NVM's poor write performance remains a severe obstacle, preventing it from being used as a DRAM alternative in the main memory. Most of the prior work targeted optimizing writes at the main memory side and neglected the decisive role of upper-level cache management policies on reducing the number of writes. In this article, we propose a novel cache management policy that attempts to maximize write-coalescing in the on-chip SRAM last-level cache (LLC) for the sake of reducing the number of costly... 

As technology process node scales down, on-chip SRAM caches lose their efficiency because of their low scalability, high leakage power, and increasing rate of soft errors. Among emerging memory technologies, Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM-based cache memories. The main advantages of STT-MRAM are its non-volatility, near-zero leakage power, higher density, soft-error immunity, and higher scalability. Despite these advantages, high error rate in STT-MRAM cells due to retention failure, write failure, and read disturbance threatens the reliability of cache memories built upon STT-MRAM technology. The error rate is significantly...