An 8-T Processing-in-Memory SRAM Cell-Based Pixel-Parallel Array Processor for Vision Chips

Vision chip is a high-speed image processing device, featuring a massively-parallel pixel-level processing element (PE) array to boost pixel processing speed. However, the collocated processing unit and fine-grained data memory unit inside each PE impose a huge requirement on memory access bandwidth as well as big area and energy consumption. To overcome this bottleneck, this paper proposes a full custom 8T SRAM-based Processing-in-Memory (PIM) architecture together with a multiplexer-based arithmetic-logic unit (mux-based ALU) to realize pixel-parallel array processor for energy-efficient vision chips. The proposed PIM architecture is constructed by embroidering each dual-port 8T SRAM cell with mux-based ALU, so as to form a PIM PE array. Each PIM PE holds a 130-bit 8T SRAM cell block embedding in-memory logic functions, of which 128-bit 8T SRAM cells serve as the PE memory, and 2-bit 8T SRAM cells act as a buffer register in the PE. A full custom physical layout of a
$128\times128$
prototyping PIM PE array is designed and evaluated using a 65 nm CMOS technology. The simulation results demonstrate that our proposed PIM PE architecture could operate under a 200 MHz clock frequency with a 1.0 V power supply, and reach a high energy efficiency of 512 GOPS/W and a high area efficiency of 29 GOPS/mm2.