Reducing access latency of MLC PCMs through line striping

Hoseinzadeh, M ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1109/ISCA.2014.6853228
  3. Abstract:
  4. Although phase change memory with multi-bit storage capability (known as MLC PCM) offers a good combination of high bit-density and non-volatility, its performance is severely impacted by the increased read/write latency. Regarding read operation, access latency increases almost linearly with respect to cell density (the number of bits stored in a cell). Since reads are latency critical, they can seriously impact system performance. This paper alleviates the problem of slow reads in the MLC PCM by exploiting a fundamental property of MLC devices: the Most-Significant Bit (MSB) of MLC cells can be read as fast as SLC cells, while reading the Least-Significant Bits (LSBs) is slower. We propose Striped PCM (SPCM), a memory architecture that leverages this property to keep MLC read latency in the order of SLC's. In order to avoid extra writes onto memory cells as a result of striping memory lines, the proposed design uses a pairing write queue to synchronize write-back requests associated with blocks that are paired in striping mode. Our evaluation shows that our design significantly improves the average memory access latency by more than 30% and IPC by up to 25% (10%, on average), with a slight overhead in memory energy (0.7%) in a 4-core CMP model running memory-intensive benchmarks
  5. Keywords:
  6. Cytology ; Memory architecture ; Access latency ; Fundamental properties ; Least significant bits ; Memory access latency ; Memory energies ; Read latencies ; Read operation ; Storage capability ; Cells
  7. Source: Proceedings - International Symposium on Computer Architecture ; Article number 6853228 , 14-18 June , 2014 , p. 277-288 ; ISSN: 10636897 ; ISBN: 9781479943968
  8. URL: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6853228&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6853228