True 4-Bit Quantized Convolutional Neural Network Training on CPU: Achieving Full-Precision Parity
arXiv:2603.13931 · March 2026
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This paper challenges the assumption that neural network training requires high precision
and expensive hardware. Using a novel tanh-based soft weight clipping technique combined
with symmetric 4-bit quantization, dynamic per-layer scaling, and straight-through
estimators, a VGG-style CNN was trained entirely from scratch on commodity CPUs with no
specialized kernels and no post-training quantization.
Results: 92.34% accuracy on CIFAR-10 (0.16% below full-precision baseline), 70.94% on
CIFAR-100, and 83.16% on a consumer Android device in 6 epochs. 8x memory compression
over FP32. Source code, training logs, and model checkpoints are open-source.
4-bit QAT
PyTorch
CNN
CPU Training
Tanh Clipping