Dynamic random access memory (DRAM) reliability has become one of the critical issues in embedded systems, as DRAM process technology advances with the increase in bit error probability. Unfortunately, redundant error-correction code (ECC) chips cannot be applied to embedded systems since cores and DRAMs are tightly coupled without a dual in-line memory module (DIMM) slot to account for the form factor, cost, and limited pin count. Therefore, ECC parities are typically placed in the same physical array where the user and system data reside. This coexistence eventually deteriorates data locality, which could be the critical factor in DRAM performance degradation. To address this issue, we propose an ECC scheme called locality-aware compression (LoComp) which integrates a compression algorithm, DRAM data layout, and memory controller especially optimized for embedded systems. We focus on the locality of the dataset and its corresponding metadata, as well as spatial data locality in the design of DRAM data layout, which reduces the number of row activations. The major feature in a compression algorithm is adjusting the misalignment of data streams caused by the data packing in many embedded systems. Moreover, we specialize the memory controller to reduce DRAM access for ECC parities and compression flags. The core technologies for the memory controller are the adoption of a set of small caches for metadata and the support of partial write operation without changing the DRAM interface. LoComp+, an enhanced version of LoComp, further reduces DRAM access for metadata by placing the metadata close to the corresponding data. In the experiment, previous works increase the DRAM access time from 68% to over twice the value compared to ECC DIMM. Whereas, LoComp and LoComp+ show reduced performance degradation by 33% and 48%, respectively. In other words, LoComp and LoComp+ substantially improved performance from between 13% and 33% compared to previous embedded ECC schemes.
|Number of pages||13|
|Journal||IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems|
|Publication status||Published - 2019 Mar|
Bibliographical noteFunding Information:
Manuscript received June 1, 2017; revised August 14, 2017 and January 12, 2018; accepted March 5, 2018. Date of publication March 23, 2018; date of current version February 18, 2019. This work was supported in part by the National Research Foundation of Korea under Grant 2016R1A2B4011799, in part by the Ministry of Trade, Industry and Energy under Grant 10080722 and the Korea Semiconductor Research Consortium Support Program for the Development of the Future Semiconductor Device, and in part by the Samsung Electronics Company Ltd., Hwasung, Korea. This paper was recommended by Associate Editor J. Henkel. (Corresponding author: Eui-Young Chung.) The authors are with the School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, South Korea (e-mail: firstname.lastname@example.org). Digital Object Identifier 10.1109/TCAD.2018.2818692
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All Science Journal Classification (ASJC) codes
- Computer Graphics and Computer-Aided Design
- Electrical and Electronic Engineering