Contemporary computer applications require more and more memory capacity as well as memory bandwidth. This is the amount of memory that can be used for applications per second. The memory capacity of RAM memories is not so much a problem, but it is the ever-increasing memory bandwidth that RAM memories are struggling with. Consequently, computer architects must look for alternative memory technologies to continue to meet the high capacity and bandwidth requirements.

"Recently introduced 3D memories, such as High-Bandwidth Memory (HBM) where several memory chips are placed on top of each other, deliver significantly higher bandwidth but have the disadvantage of limited capacity and inferior reliability compared to conventional RAM memories," explains Wenjie.

"In order to circumvent the limitations of different memory technologies, researchers have developed hybrid memories where, for example, a 3D memory is combined with a RAM memory. This allows high bandwidth (thanks to the 3D memory) and high capacity (thanks to the RAM memory) to be offered. However, the reliability of hybrid memories is limited by the weakest link, which is the 3D memory," says Wenjie.

"A concrete practical problem in the exploration and evaluation of hybrid memory systems is that existing simulation methods are inadequate. Simulation times increase exponentially with system size, and in some cases it is even impossible due to simulation infrastructure limitations," she continues.

"In my research, I have been looking for improvements in terms of performance and reliability of hybrid memories and in terms of simulating large systems," she concludes.

Read a more detailed summary or the entire PhD

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PhD Title: Reliability-Aware Management in Hybrid Memories: Evaluation through Scale-Model Simulation

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Wenjie Liu obtained her Master degree in Computer Science from the National University of Defense Technology in China in 2017. She started her PhD with a CSC scholarship at Ghent University under the supervision of Prof. Lieven Eeckhout in the same year. Her Ph.D. research produced two publications in peer-reviewed A1 journals and one conference publication. Her research focuses in the area of computer architecture, with particular emphasis on architectural simulation and reliability optimization of hybrid memory system. She proposes reliability-aware garbage collection to improve performance and reliability of hybrid memories and scale-model simulation to predict performance for a future large-scale system.

Contact: Wenjie Liu, Lieven Eeckhout

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Editor: Jeroen Ongenae - Illustrator: Roger Van Hecke