Using adaptive read voltage thresholds to enhance the reliability of MLC NAND flash memory systems

2021 ◽

Vol 12 (5) ◽

pp. 209-215

Author(s):

Myungsub Lee

Keyword(s):

Performance Evaluation ◽

Standard Deviation ◽

Flash Memory ◽

Garbage Collection ◽

Memory Systems ◽

Nand Flash ◽

Nand Flash Memory ◽

Wear Leveling ◽

Block Classification ◽

Update Frequency

In this paper, we propose a block classification with monitor and restriction (BCMR) method to isolate and reduce the interference of blocks in garbage collection and wear leveling. The proposed method monitors the endurance variation of blocks during garbage collection and detects hot blocks by making a restriction condition based on this information. This method induces block classification by its update frequency for garbage collection and wear leveling, resulting in a prolonged lifespan for NAND flash memory systems. The performance evaluation results show that the BCMR method prolonged the life of NAND flash memory systems by 3.95% and reduced the standard deviation per block by 7.4%, on average.

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Temperature Impacts on Endurance and Read Disturbs in Charge-Trap 3D NAND Flash Memories

Micromachines ◽

10.3390/mi12101152 ◽

2021 ◽

Vol 12 (10) ◽

pp. 1152

Author(s):

Fei Chen ◽

Bo Chen ◽

Hongzhe Lin ◽

Yachen Kong ◽

Xin Liu ◽

...

Keyword(s):

Flash Memory ◽

Temperature Effects ◽

Memory Systems ◽

Nand Flash ◽

Nand Flash Memory ◽

Flash Memories ◽

Charge Trap ◽

Fundamental Factor ◽

Temperature Impacts ◽

Raw Bit Error Rate

Temperature effects should be well considered when designing flash-based memory systems, because they are a fundamental factor that affect both the performance and the reliability of NAND flash memories. In this work, aiming to comprehensively understanding the temperature effects on 3D NAND flash memory, triple-level-cell (TLC) mode charge-trap (CT) 3D NAND flash memory chips were characterized systematically in a wide temperature range (−30~70 °C), by focusing on the raw bit error rate (RBER) degradation during program/erase (P/E) cycling (endurance) and frequent reading (read disturb). It was observed that (1) the program time showed strong dependences on the temperature and P/E cycles, which could be well fitted by the proposed temperature-dependent cycling program time (TCPT) model; (2) RBER could be suppressed at higher temperatures, while its degradation weakly depended on the temperature, indicating that high-temperature operations would not accelerate the memory cells’ degradation; (3) read disturbs were much more serious at low temperatures, while it helped to recover a part of RBER at high temperatures.

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A Relative Reference Responsive LRU based Page Replacement Algorithm for NAND Flash Memory

Webology ◽

10.14704/web/v18i1/web18027 ◽

2021 ◽

Vol 18 (1) ◽

pp. 62-76

Author(s):

Hitha Paulson ◽

Dr.R. Rajesh

Keyword(s):

Flash Memory ◽

Memory Systems ◽

Management Technique ◽

Hard Disks ◽

Nand Flash ◽

Nand Flash Memory ◽

Replacement Algorithm ◽

Replacement Procedure ◽

Replacement Algorithms ◽

Fast Access

The acceptance of NAND flash memories in the electronic world, due to its non-volatility, high density, low power consumption, small size and fast access speed is hopeful. Due to the limitations in life span and wear levelling, this memory needs special attention in its management techniques compared to the conventional techniques used in hard disks. In this paper, an efficient page replacement algorithm is proposed for NAND flash based memory systems. The proposed algorithm focuses on decision making policies based on the relative reference ratio of pages in memory. The size adjustable eviction window and the relative reference based shadow list management technique proposed by the algorithm contribute much to the efficiency in page replacement procedure. The simulation tool based experiments conducted shows that the proposed algorithm performs superior to the well-known flash based page replacement algorithms with regard to page hit ratio and memory read/write operations.

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