Search

Transformer neural networks, driven by self-attention mechanisms, are core components of foundational and Large Language Models. In generative transformers, self-attention uses cache memory to store token projections, avoiding recomputation at each time step. However, GPU-stored projections must be loaded into SRAM for each new generation step, causing latency and energy bottlenecks for long sequences. In this work, we propose a fast and energy-efficient hardware implementation of self-attention using analog in-memory computing based on gain cell memories. Volatile gain cell memories can be efficiently written to store new tokens during sequence generation, while performing analog signed weight multiplications to compute the dot-products required for self-attention. We implement Sliding Window Attention, which keeps memory of a finite set of past steps. A charge-to-pulse converter for array readout eliminates the need for analog-to-digital conversion between self-attention stages. Using a co-designed initialization algorithm to adapt pre-trained weights to gain cell non-idealities, we achieve NLP performance comparable to ChatGPT-2 with minimal training iterations, despite hardware constraints. Our end-to-end hardware design includes digital controls, estimating area, latency, and energy. The system reduces attention latency by up to two orders of magnitude and energy consumption by up to five orders compared to GPUs, marking a significant step toward ultra-fast, low-power sequence generation in Large Language Models., Comment: 25 pages, 6 figures, 1 table

Emerging non-volatile memories (NVMs) represent a disruptive technology that allows a paradigm shift from the conventional von Neumann architecture towards more efficient computing-in-memory (CIM) architectures. Several instrumentation platforms have been proposed to interface NVMs allowing the characterization of single cells and crossbar structures. However, these platforms suffer from low flexibility and are not capable of performing CIM operations on NVMs. Therefore, we recently designed and built the NeuroBreakoutBoard, a highly versatile instrumentation platform capable of executing CIM on NVMs. We present our preliminary results demonstrating a relative error < 5% in the range of 1 k$\Omega$ to 1 M$\Omega$ and showcase the switching behavior of a HfO$_2$/Ti-based memristive cell.