Energy-Aware Designs of Ferroelectric Ternary Content Addressable Memory
Yu Qian1, Zhenhao Fan1, Haoran Wang1, Chao Li1, Mohsen Imani2, Kai Ni3, Grace Li Zhang4, Bing Li4, Ulf Schlichtmann4, Cheng Zhuo1,a and Xunzhao Yin1,b
1Zhejiang University, Hangzhou, China
aczhuo@zju.edu.cn
bxyin1@zju.edu.cn
2University of California, Irvine, USA
3Rochester Institute of Technology, USA
4Technical University of Munich, Germany
ABSTRACT
Ternary content addressable memories (TCAMs) are a special form of computing-in-memory (CiM) circuits that aim to address the so-called memory wall issues by merging the parallel search function with memory blocks. Due to the content addressing nature, TCAMs have been widely utilized for search intensive tasks in low-power, data analytic applications,such as IP routers, associative memories, and learning models. While most state-of-the-art TCAM designs focus on improving the TCAM density by harnessing compact nonvolatile memories (NVMs), little efforts have been spent on reducing and optimizing the energy consumption of the NVM based TCAM. In this paper, by exploiting the Ferroelectric FET (FeFET) as a representative NVM, we propose two compact and energy-aware designs of ferroelectric TCAMs for low power applications. We first introduce a novel 2FeFET based XOR-like gate structure that can also be adopted to other NVMs, and then leverage the structure to propose two TCAM designs that achieve high energy efficiency by either reducing the associated precharge overhead (2FeFET-1T cell), or eliminating the precharge phase typically required by TCAMs (2FeFET-2T cell). We evaluate and compare the designs w.r.t area, search energy and delay at array level with other existing designs, and benchmark the proposed TCAM designs in an associative memory based GPU architecture. The results suggest that the proposed 2FeFET- 1T/2FeFET-2T TCAM design consumes 3.03X/8.08X less search energy than the conventional 16T CMOS TCAM, while the proposed design cell area is only 32.1%/39.3% of the latter. Compared with the state-of-the-art 2FeFET only TCAM array, our proposed designs still achieve 1.79X and 4.79X search energy reduction, respectively. Moreover, our proposed designs can achieve, on average, 45.2%/51.5% energy saving compared with the conventional GPU based architecture at the application level.
