X-pSRAM: A Photonic SRAM with Embedded XOR Logic for Ultra-Fast In-Memory Computing

TL;DR

This paper introduces X-pSRAM, a photonic memory device capable of ultra-fast in-memory XOR computation at 10 GHz, significantly reducing latency and energy consumption for data-intensive applications.

Contribution

It presents a novel electro-optic pSRAM bitcell with integrated XOR logic using microring resonators, enabling high-speed optical in-memory computing with parallel processing capabilities.

Findings

Achieves 10 GHz read, write, and XOR compute operations in optical domain.

Consumes only 13.2 fJ per bit for XOR operation, demonstrating high energy efficiency.

Supports massively parallel XOR operations via wavelength-division multiplexing.

Abstract

Traditional von Neumann architectures suffer from fundamental bottlenecks due to continuous data movement between memory and processing units, a challenge that worsens with technology scaling as electrical interconnect delays become more significant. These limitations impede the performance and energy efficiency required for modern data-intensive applications. In contrast, photonic in-memory computing presents a promising alternative by harnessing the advantages of light, enabling ultra-fast data propagation without length-dependent impedance, thereby significantly reducing computational latency and energy consumption. This work proposes a novel differential photonic static random access memory (pSRAM) bitcell that facilitates electro-optic data storage while enabling ultra-fast in-memory Boolean XOR computation. By employing cross-coupled microring resonators and differential photodiodes, the XOR-augmented pSRAM (X-pSRAM) bitcell achieves at least 10 GHz read, write, and compute operations entirely in the optical domain. Additionally, wavelength-division multiplexing (WDM) enables n-bit XOR computation in a single-shot operation, supporting massively parallel processing and enhanced computational efficiency. Validated on GlobalFoundries' 45SPCLO node, the X-pSRAM consumed 13.2 fJ energy per bit for XOR computation, representing a significant advancement toward next-generation optical computing with applications in cryptography, hyperdimensional computing, and neural networks.