Approximate Priority Hybrid 3DNoC Buffered-Bufferless Router

Abstract

This paper introduces a novel 3D NoC router that combines buffered and bufferless routing with approximate priority comparison when deflecting flits. Our proposal is a modification of an asymmetrical router that is buffered in the z dimension ports and bufferless in the x and y dimension ports. Flits that request output ports in the x and y dimensions are granted or deflected based on approximate, instead of accurate, priority comparison. Experimental results show that the proposed router, in addition to effectively combining the advantages of both buffered and bufferless routers, achieves additional performance and area gains due to the reduced logic required for approximate priority comparison in flit deflections. Experimental results using synthetic and realistic traffic show that the proposed router begins to saturate at a significantly higher injection rate than a bufferless router, but at a slightly lower injection rate than when using accurate priority comparison. Furthermore, the proposed router achieves higher clock frequencies and a reduced area compared to bufferles routers due to the simpler permutation network. The increased routing efficiency is shown to also translate to energy gains.

Keywords

• 3D Networks-on-Chip
• NoC
• bufferless routing
• approximate computing