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The Hybrid Memory Cube (HMC) is a 3-D-stacked DRAM architecture whose I/O interface achieves up to 320 GB/s of external bandwidth. Therefore, the HMC is a promising alternative to DDRx memory due to its potential to achieve substantially improved memory bandwidth. However, the high price of a HMC device compromises cost efficiency when the device is lightly utilized. The cost of a HMC device with 2GB capacity is about 5 times of a DDRx memory with the same capacity. In this paper, we propose a new inexpensive HMC+DRAM hybrid main memory architecture to reduce the cost consumption. In order to manage such hybrid memories, we develop a LRU-based data distribution mechanism to determine the destination of particular data flow. Evaluations show that our scheme reduces the cost consumption of Main Memory by 48% on average with a negligible performance degradation compared to a current HMC-based system. Also, our architecture outperforms a current DRAM-based system by 1.5 times, and reduces the response delay by 1.2 times.

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