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arXiv · 2605.28208

FCDC: Nonvolatile Charge-Domain Attention with HZO Ferroelectric Capacitors

Fares Abouagor
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Abstract

Transformer decoding is increasingly constrained by the key-value (KV) cache it must keep resident and re-read across a long session. We present the Ferroelectric Charge-Domain Compute Cell (FCDC), a hafnium-zirconium-oxide (HZO) memcapacitor that stores analog weights as nonvolatile remanent polarization and performs charge-domain vector-matrix multiplication for attention. A full-substrate mode (all q,k,v,o projections and both attention matmuls on FCDC) provides the harder noise test and upper-bounds a narrower KV-coprocessor serving mode. The evaluation is simulation-based (no FCDC device is fabricated), cross-checked across four simulators, and anchored to wafer-scale 10nm-HZO measurements. Across 12 pretrained LLMs (dense to Qwen3-32B fully substituted, plus a 141B Mixtral-8x22B stress test), all-layer noise substitution adds +2.6% WikiText-2 perplexity on Qwen3-32B and +2.9% (five-seed mean) on Mistral-7B-v0.3; five downstream tasks stay within 5% of digital, the deltas hold to 128k context, and the serving mode costs under 0.5% at 7-8B. Analog-input fragility localizes to the value projection, and periphery-side input dithering recovers the worst-case PWM-nonlinearity collapse to near-baseline without retraining. The advantage is not raw multiply-accumulate energy, where the FCDC tile merely matches switched-capacitor SRAM compute-in-memory. It is nonvolatility, no refresh, and KV-cache residency. On measured INT4 decode energy, a workload simulator projects 18-35x lower per-served-token energy on retrieval-augmented generation and agent loops than a single-user GPU, narrowing to 1.4-4.7x against optimized serving baselines (batched vLLM, offload, power-gating) but exceeding 40x on multi-hour parked sessions. Long-residency, persistent-KV serving is the regime where a nonvolatile charge-domain substrate holds a durable advantage over an optimized GPU.

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Fares Abouagor. 2026-05-27. FCDC: Nonvolatile Charge-Domain Attention with HZO Ferroelectric Capacitors. https://arxiv.org/abs/2605.28208

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