CompAir: Synergizing Complementary PIMs and In-Transit NoC Computation for Efficient LLM Acceleration

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Hauptverfasser: Li, Hongyi, Ma, Songchen, Qu, Huanyu, Zhang, Weihao, Chen, Jia, Lin, Junfeng, Tu, Fengbin, Zhao, Rong
Format: Preprint
Veröffentlicht: 2025
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author Li, Hongyi
Ma, Songchen
Qu, Huanyu
Zhang, Weihao
Chen, Jia
Lin, Junfeng
Tu, Fengbin
Zhao, Rong
author_facet Li, Hongyi
Ma, Songchen
Qu, Huanyu
Zhang, Weihao
Chen, Jia
Lin, Junfeng
Tu, Fengbin
Zhao, Rong
contents The rapid advancement of Large Language Models (LLMs) has revolutionized various aspects of human life, yet their immense computational and energy demands pose significant challenges for efficient inference. The memory wall, the growing processor-memory speed disparity, remains a critical bottleneck for LLM. Process-In-Memory (PIM) architectures overcome limitations by co-locating compute units with memory, leveraging 5-20$\times$ higher internal bandwidth and enabling greater energy efficiency than GPUs. However, existing PIMs struggle to balance flexibility, performance, and cost-efficiency for LLMs' dynamic memory-compute patterns and operator diversity. DRAM-PIM suffers from inter-bank communication overhead despite its vector parallelism. SRAM-PIM offers sub-10ns latency for matrix operation but is constrained by limited capacity. This work introduces CompAir, a novel PIM architecture that integrates DRAM-PIM and SRAM-PIM with hybrid bonding, enabling efficient linear computations while unlocking multi-granularity data pathways. We further develop CompAir-NoC, an advanced network-on-chip with an embedded arithmetic logic unit that performs non-linear operations during data movement, simultaneously reducing communication overhead and area cost. Finally, we develop a hierarchical Instruction Set Architecture that ensures both flexibility and programmability of the hybrid PIM. Experimental results demonstrate that CompAir achieves 1.83-7.98$\times$ prefill and 1.95-6.28$\times$ decode improvement over the current state-of-the-art fully PIM architecture. Compared to the hybrid A100 and HBM-PIM system, CompAir achieves 3.52$\times$ energy consumption reduction with comparable throughput. This work represents the first systematic exploration of hybrid DRAM-PIM and SRAM-PIM architectures with in-network computation capabilities, offering a high-efficiency solution for LLM.
format Preprint
id arxiv_https___arxiv_org_abs_2509_13710
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle CompAir: Synergizing Complementary PIMs and In-Transit NoC Computation for Efficient LLM Acceleration
Li, Hongyi
Ma, Songchen
Qu, Huanyu
Zhang, Weihao
Chen, Jia
Lin, Junfeng
Tu, Fengbin
Zhao, Rong
Hardware Architecture
The rapid advancement of Large Language Models (LLMs) has revolutionized various aspects of human life, yet their immense computational and energy demands pose significant challenges for efficient inference. The memory wall, the growing processor-memory speed disparity, remains a critical bottleneck for LLM. Process-In-Memory (PIM) architectures overcome limitations by co-locating compute units with memory, leveraging 5-20$\times$ higher internal bandwidth and enabling greater energy efficiency than GPUs. However, existing PIMs struggle to balance flexibility, performance, and cost-efficiency for LLMs' dynamic memory-compute patterns and operator diversity. DRAM-PIM suffers from inter-bank communication overhead despite its vector parallelism. SRAM-PIM offers sub-10ns latency for matrix operation but is constrained by limited capacity. This work introduces CompAir, a novel PIM architecture that integrates DRAM-PIM and SRAM-PIM with hybrid bonding, enabling efficient linear computations while unlocking multi-granularity data pathways. We further develop CompAir-NoC, an advanced network-on-chip with an embedded arithmetic logic unit that performs non-linear operations during data movement, simultaneously reducing communication overhead and area cost. Finally, we develop a hierarchical Instruction Set Architecture that ensures both flexibility and programmability of the hybrid PIM. Experimental results demonstrate that CompAir achieves 1.83-7.98$\times$ prefill and 1.95-6.28$\times$ decode improvement over the current state-of-the-art fully PIM architecture. Compared to the hybrid A100 and HBM-PIM system, CompAir achieves 3.52$\times$ energy consumption reduction with comparable throughput. This work represents the first systematic exploration of hybrid DRAM-PIM and SRAM-PIM architectures with in-network computation capabilities, offering a high-efficiency solution for LLM.
title CompAir: Synergizing Complementary PIMs and In-Transit NoC Computation for Efficient LLM Acceleration
topic Hardware Architecture
url https://arxiv.org/abs/2509.13710