Prism ML Website |
White Paper |
Demo & Examples |
Discord
Ternary-Bonsai-8B-mlx-2bit
Ternary (1.58-bit) language model for Apple Silicon
7.1x smaller than FP16 | 5.2x faster on M4 Pro | 27 tok/s on iPhone | runs on Mac, iPhone, iPad
Highlights
- 2.15 GiB (2.30 GB) packed 2-bit size (down from 16.38 GB FP16) — runs comfortably on any Mac or iPhone
- Ternary weights {-1, 0, +1} across embeddings, attention projections, MLP projections, and LM head
- 75.5 avg benchmark score across 6 categories — competitive with full-precision 8B models at 1/9th the size
- 5-point improvement over our earlier 1-bit Bonsai 8B (70.5) at only ~0.6 GB additional footprint
- MLX-native format with group size 128 and FP16 scaling
Resources
- White Paper
- Demo repo — examples for serving, benchmarking, and integrating Bonsai
- Discord — community support and updates
- Kernels: MLX (Apple Silicon) · mlx-swift (iOS/macOS) — 2-bit format is supported out of the box
Model Overview
Quantization Format: Ternary g128
Each weight takes a value from {-1, 0, +1}, with one shared FP16 scale per group of 128 weights:
The information-theoretic cost is log2(3) ≈ 1.585 bits per weight, plus FP16 group scales (16 bits per 128 weights), for a theoretical minimum of ~1.71 bits/weight. This release uses the MLX 2-bit format, which stores each ternary value in 2 bits plus group scales, for an effective ~2.125 bits/weight.
The addition of a zero value compared to binary (1-bit) provides more expressive weight representations, allowing better preservation of model quality under extreme compression.
Memory
Quickstart
MLX (Python)
MLX Swift (iOS / macOS)
Ternary Bonsai 8B runs natively on iPhone and iPad via MLX Swift at 27 tok/s on iPhone 17 Pro Max. The 2-bit format is supported out of the box.
Throughput (MLX / Apple Silicon)
iPhone 17 Pro Max (MLX Swift)
Benchmarks
Evaluated with EvalScope v1.4.2 + vLLM 0.15.1 on NVIDIA H100 under identical infrastructure, generation parameters, and scoring. All models are in the 6B-9B parameter range.
Ternary Bonsai 8B ranks 2nd among all compared models despite being 1/9th the size.
Intelligence Density
Limitations
- Only MLX 2-bit format is available at initial release; more formats for other backends coming soon
- Mobile power measurement is estimated rather than hardware-metered
- The full-precision frontier continues to advance; the ternary methodology is architecture-agnostic
Citation
Contact
For questions, feedback, or collaboration inquiries: contact@prismml.com