Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.19277

TALU: A Reconfigurable Tiled-ALU Grid for RISC-V

Ali Emre Oztas·Can Erim Karsal·Mahir Demir·Mikel Luján
View original source ↗Read source document ↗Export metadata ↓

Abstract

Lane-based RISC-V vector processors exploit data parallelism well but pay a recurring cost for two common patterns: reductions, which require a separate tree pass, and deep dependent expression chains, which cannot be fused and are issued as serial vector instructions. We present TALU, a 5-stage RISC-V core whose execute stage is an NxN grid of registered ALU tiles instead of a single ALU. The grid is a reconfigurable, feed-forward spatial fabric: tiles route operands only from non-backward neighbours, and added diagonal forwarding lets a reduction collapse spatially. A minimal custom extension configures the per-tile operation, routing, and per-tile constants, and streams operands through the array. On a single fabric, TALU runs ordinary scalar code, single deep-path expressions, and multi-lane vector kernels. On the benchmark suite of the RISC-V2 vector processor, TALU is 1.8-5.5x faster than RISC-V2 and 4.5-15.5x faster than Vicuna at equal lane count, with a reduction cost (dot÷add) of 1.05x versus 1.96x and 1.26x for the vector cores. A retimed implementation places and routes at 1.03 GHz in 45 nm in 0.30 mm2, half the area of RISC-V2.

Explore related subjects

cs.AR

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Ali Emre Oztas, Can Erim Karsal, Mahir Demir, Mikel Luján. 2026-10-13. TALU: A Reconfigurable Tiled-ALU Grid for RISC-V. https://arxiv.org/abs/2610.19277

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

LUTstructions: Fast-Reconfigurable FPGA-Based Instructions

General-purpose processors feature a limited number of instructions based on an instruction set. They can be numerous, such as with vector extensions that include hundreds or thousands of instructions, but this comes at a cost; they are often unable to express arbitrary tasks efficiently. This paper explores the concept of having reconfigurable instructions by incorporating reconfigurable areas in a softcore. It follows a relatively new computing paradigm for seamlessly loading instruction implementation-carrying bitstreams from main memory. The resulting softcore is entirely evaluated on an FPGA, essentially having an FPGA-on-FPGA for the instruction implementations, with no notable operating frequency overhead. This is achieved with a custom FPGA architecture, which is tailored towards low-latency for custom instructions and wide reconfiguration, as well as a soft implementation for the purposes of architectural exploration. All code is open-source to foster further research on reconfigurable instructions.

cs.AR↗
arXiv2026

Interflow: Breaking the Offline-Online Barrier for Private AI at the Edge

Privacy-preserving machine learning (PPML) offers a promising path toward bringing powerful AI services to the edge without exposing sensitive user data. However, its practical deployment remains constrained by the high communication, computation, and data-movement costs of secure multi-party computation (MPC), particularly during nonlinear inference. Existing MPC systems typically decouple input-independent correlated randomness generation from online execution, creating substantial memory pressure to buffer single-use cryptographic data. Moreover, limited storage can force a stop-and-refill execution pattern that repeatedly stalls the pipeline to replenish these buffers, bringing randomness generation back onto the critical path. We propose Interflow, an algorithm-hardware co-design that rethinks this separation by batch-wise processing and pipelining correlated-randomness generation with online execution: while the current batch consumes pre-generated randomness to execute secure nonlinear operations, correlation generation proceeds concurrently for the next batch. By leveraging interleaved execution, efficient data movement, and hardware acceleration, the design transforms preprocessing from a serialized, storage-intensive offline phase into a continuously overlapped pipeline that generates correlated randomness closer to the point of consumption, reducing memory footprint and data movement overhead. Implemented on the Zynq UltraScale+ ZCU102, Interflow improves nonlinear evaluation throughput by up to 1.55x for CNN operators and 1.48x for transformer operators. It achieves up to 1.26x speedup for ResNet-50 and up to 1.21x speedup for BERT-base, and reduces memory footprint by up to 37%, compared with baseline frameworks.

cs.AR↗
arXiv2026

ZKPU: Zero-Knowledge Processing Unit for Heterogeneous Workloads

Zero-knowledge proofs (ZKPs) have become a fundamental building block for privacy-preserving computation, blockchain systems, and verifiable machine learning. Modern ZKP protocols span two distinct families: curve-based protocols, which rely on large finite-field arithmetic, and hash-based protocols, which operate over native 64-bit fields. Existing hardware accelerators are specialized for one protocol family because they are built on operand-scanning Montgomery multiplication, resulting in fixed-width datapaths, poor utilization across heterogeneous operand widths, and limited scalability. This paper presents \emph{ZKPU}, a Zero-Knowledge Processing Unit for heterogeneous ZKP workloads. ZKPU introduces a new compute paradigm by co-designing finely integrated product scanning (FIPS) Montgomery multiplication with a reconfigurable Twin Systolic Fabric (TSF), enabling modular multiplication at arbitrary widths in 64-bit increments. Combined with a fine-grained Deque buffer, on-chip twiddle-factor generator, and memory-efficient MSM preprocessing strategy, ZKPU provides a unified architecture for both curve-based and hash-based protocols. Evaluation using Groth16 and Plonky2 shows that ZKPU achieves up to $144\times$ speedup for NTT, $13.6\times$ for MSM, and approximately $7.2\times$ end-to-end application speedup over state-of-the-art accelerators, while being the first architecture to efficiently support both protocol families on a single reconfigurable hardware platform.

cs.AR↗