Efficient Implementation of Many-Ported Memories by Using Standard-Cell Memory Approach

Abstract

Multi-ported memories are widely used in many applications, such as for high-speed and high-performance parallel computations. While conventional SRAM-based memory macros are limited in both flexibility (e.g., to accommodate a large number of write inputs and read outputs) and performance, standard cell-based memories are much more flexible and can be parameterized. The physical implementation approaches of the existing tools have great difficulty in dealing with these memories due to the multiplicity of wiring and misunderstanding of the regular structure of these arrays, to the point of inability to converge under certain conditions. This paper presents novel methodologies for the logical and physical implementation of many-ported standard cell memories (MPSCMs). Two methodologies are proposed to replace the standard design flow by controlling and guiding the design tools to improve power consumption, area and performance of these arrays. A commercial 65 nm CMOS technology was used to evaluate and benchmark the two design methodologies on MPSCM macros of different sizes as compared to other equivalent macros designed with standard methodologies and state-of-the-art designs. Physical implementation results show that as compared to a standard RTL approach, the implementation of a 3-write, 5-read port (3W5R) register file with the tightly-controlled methodology leads a $2\times $ increase in placement density along with significant reductions in write power (–66%), read power (–37%) and leakage power (–80%), while also improving the access time (–6%). When considering an extreme case of a many-ported memory with 20-write and 20-read ports (20W/20R), the guided methodology leads to improvements in delay (–13%), write power (–62%), and leakage power (–51%). Both methodologies were implemented within an automation utility based on the “Salamandra” open source netlisting tool, enabling fast and easy migration to additional process nodes and standard cell libraries for generating MPSCMs with various sizes and features.

Keywords

• Standard cell memories (SCMs)
• multi-ported memories
• controlled placement
• low-power
• vector register file
• register file