Browsing by Author "Ma, Yu-Ping"

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Flash Read Disturb Management Using Adaptive Cell Bit-Density with In-Place Reprogramming
(2018-01-01)
Wu, Tai-Chou
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Ma, Yu-Ping
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Chang, Li-Pin
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資訊工程學系
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Department of Computer Science
Read disturbance is a circuit-level noise induced by flash read operations. Read refreshing employs data migration to prevent read disturbance from corrupting useful data. However, it costs frequent block erasure under read-intensive workloads. Inspired by software-controlled cell bit-density, we propose to reserve selected threshold voltage levels as guard levels to extend the tolerance of read disturbance. Blocks with guard levels have a low cell bit-density, but they can store frequently read data without frequent read refreshing. We further propose to convert a high-density block into a low-density one using in place reprogramming to reduce the need for data migration. Our approach reduced the number of blocks erased due to read refreshing by up to 85% and the average read response time by up to 22%.