majentik/gemma-4-31B-it-RotorQuant-MLX-4bit

Gemma 4 31B-it - RotorQuant MLX 4-bit

4-bit weight-quantized MLX version of google/gemma-4-31B-it with RotorQuant KV-cache quantization. Optimized for Apple Silicon inference via the MLX framework. RotorQuant delivers 5.3x faster prefill and 28% faster decode compared to TurboQuant. A good balance between model quality and memory efficiency.

Approximate model size: ~17 GB

Model Specifications

Property	Value
Base Model	google/gemma-4-31B-it
Parameters	31 billion
Architecture	Dense transformer
Modality	Multimodal: image + text input, text output
License	Apache 2.0
Weight Quantization	4-bit (~17 GB)
KV-Cache Quantization	RotorQuant
Framework	MLX (Apple Silicon)

Quickstart

import mlx.core as mx
from mlx_lm import load, generate

model, tokenizer = load("majentik/gemma-4-31B-it-RotorQuant-MLX-4bit")

prompt = "Describe this image in detail."
response = generate(model, tokenizer, prompt=prompt, max_tokens=512)
print(response)

For multimodal usage with images:

from mlx_vlm import load, generate

model, processor = load("majentik/gemma-4-31B-it-RotorQuant-MLX-4bit")

prompt = "What do you see in this image?"
output = generate(model, processor, prompt=prompt, image="path/to/image.jpg", max_tokens=512)
print(output)

What is RotorQuant?

RotorQuant is a high-performance KV-cache quantization method that achieves significantly better throughput than TurboQuant. Combined with 4-bit weight quantization in MLX, this provides a dual compression strategy with superior KV-cache performance: smaller model weights plus faster compressed KV cache for efficient long-context generation.

Key advantages over TurboQuant:

• 5.3x faster prefill
• 28% faster decode
• Equivalent memory savings

KV-Cache Quantization Comparison

Method	Prefill Speed	Decode Speed	Memory Savings	Reference
TurboQuant	1x (baseline)	1x (baseline)	High	arXiv: 2504.19874
RotorQuant	5.3x faster	28% faster	High	GitHub

Memory Estimates (Gemma 4 31B-it)

Precision	Approximate Size	MLX Variant
FP16 (original)	~62 GB	--
8-bit quantized	~31 GB	RotorQuant-MLX-8bit
4-bit quantized	~17 GB	This model
2-bit quantized	~9 GB	RotorQuant-MLX-2bit

Hardware Requirements

This model requires approximately 17 GB of unified memory. Recommended hardware:

• Apple M2 Max (32 GB+)
• Apple M3 Pro (36 GB+)
• Apple M4 Pro (24 GB+)
• Any Apple Silicon Mac with 24 GB+ unified memory

See Also

• google/gemma-4-31B-it -- Base model
• majentik/gemma-4-31B-it-RotorQuant -- RotorQuant KV-cache only (transformers)
• majentik/gemma-4-31B-it-RotorQuant-MLX-8bit -- MLX 8-bit variant
• majentik/gemma-4-31B-it-RotorQuant-MLX-2bit -- MLX 2-bit variant
• majentik/gemma-4-31B-it-TurboQuant-MLX-4bit -- TurboQuant MLX 4-bit variant
• RotorQuant GitHub
• MLX Framework

Quant trade-off (MLX lane)

Bits	Approx size	Use case	Recommendation
2-bit	~8.1 GB	Aggressive quantization	Very low-RAM Macs
3-bit	~11 GB	Lossy but small	Low-RAM Macs
4-bit	~13 GB	Balanced default	Recommended for most Macs
5-bit	~16 GB	Higher fidelity	Quality-sensitive
6-bit	~19 GB	Approaching FP16 quality	High-fidelity
8-bit	~24 GB	Near-lossless reference	Fidelity-critical work

(Current variant — 4bit — is bolded.)

Variants in this family

(Showing 18 sibling variants under majentik/gemma4-31b-it-*. The current variant — RotorQuant-MLX-4bit — is bolded.)

Variant	Runtime	Approx size	Use case
RotorQuant	runtime modifier	n/a	KV-cache root (weight-agnostic)
RotorQuant-AWQ-4bit	transformers	~19 GB	GPU 4-bit (AutoAWQ)
RotorQuant-AWQ-8bit	transformers	~34 GB	GPU 8-bit (AutoAWQ)
RotorQuant-GGUF-IQ4_XS	llama.cpp	~27 GB	Lossy 4-bit, low-RAM CPU/edge
RotorQuant-GGUF-Q2_K	llama.cpp	~19 GB	Lossy, low-RAM CPU/edge
RotorQuant-GGUF-Q3_K_M	llama.cpp	~24 GB	Smaller 3-bit, CPU-friendly
RotorQuant-GGUF-Q4_K_M	llama.cpp	~34 GB	Balanced default
RotorQuant-GGUF-Q5_K_M	llama.cpp	~41 GB	Higher fidelity, more RAM
RotorQuant-GGUF-Q8_0	llama.cpp	~65 GB	Near-lossless reference
RotorQuant-MLX-2bit	mlx-lm	~9.9 GB	Apple Silicon, smallest
RotorQuant-MLX-4bit	mlx-lm	~19 GB	Apple Silicon balanced
RotorQuant-MLX-8bit	mlx-lm	~37 GB	Apple Silicon reference
TurboQuant	runtime modifier	n/a	KV-cache root (weight-agnostic)
TurboQuant-AWQ-4bit	transformers	~19 GB	GPU 4-bit (AutoAWQ)
TurboQuant-AWQ-8bit	transformers	~34 GB	GPU 8-bit (AutoAWQ)
TurboQuant-MLX-2bit	mlx-lm	~9.9 GB	Apple Silicon, smallest
TurboQuant-MLX-4bit	mlx-lm	~19 GB	Apple Silicon balanced
TurboQuant-MLX-8bit	mlx-lm	~37 GB	Apple Silicon reference