How fast will GPT-OSS 20B feel on the CPU-only (Ryzen 9 9950X, 96GB DDR5)?

GPT-OSS 20B on the CPU-only (Ryzen 9 9950X, 96GB DDR5)

GPT-OSS 20B is a 20.91B-parameter mixture-of-experts model (3.6B active per token). At MXFP4 it needs about 12.9 GB of memory. The CPU-only (Ryzen 9 9950X, 96GB DDR5) has 89 GB usable, so it fits entirely in memory. Expect about 29 tokens/sec (23–36), with the first token after 0.4 s for a short prompt. This estimate is interpolated from benchmarks of similar setups.

Speed by quantization

Quantization	File size	Memory	Generation	First token	Source
MXFP4	12.1 GB	Fits	29 tok/s	0.4 s	Derived

GPT-OSS 20B on other hardware

H100 80GB (cloud) · 648 tok/s at MXFP4
A100 80GB (cloud) · 394 tok/s at MXFP4
NVIDIA RTX 5090 32GB · 347 tok/s at MXFP4
NVIDIA RTX PRO 6000 96GB · 347 tok/s at MXFP4
H200 141GB (cloud) · 306 tok/s at MXFP4
AMD RX 7900 XTX 24GB · 288 tok/s at MXFP4
Mac Studio M5 Ultra 512GB · 272 tok/s at MXFP4
Mac Studio M3 Ultra 512GB · 204 tok/s at MXFP4
NVIDIA RTX 4090 24GB · 195 tok/s at MXFP4
NVIDIA RTX 5080 16GB · 186 tok/s at MXFP4
NVIDIA RTX 3090 24GB · 181 tok/s at MXFP4
NVIDIA RTX 5070 Ti 16GB · 173 tok/s at MXFP4
AMD Radeon AI PRO R9700 32GB · 159 tok/s at MXFP4
MacBook Pro M5 Max 128GB · 139 tok/s at MXFP4
Mac Studio M4 Max 128GB · 136 tok/s at MXFP4
NVIDIA RTX 4070 Ti Super 16GB · 130 tok/s at MXFP4
AMD RX 7900 XT 20GB · 124 tok/s at MXFP4
AMD RX 9070 XT 16GB · 122 tok/s at MXFP4
NVIDIA RTX 5060 Ti 16GB · 87 tok/s at MXFP4
MacBook Pro M5 Pro 48GB · 82 tok/s at MXFP4
MacBook M3 Max 48GB · 81 tok/s at MXFP4
Intel Arc Pro B70 32GB · 76 tok/s at MXFP4
NVIDIA RTX 4070 12GB · 74 tok/s at MXFP4
AMD Ryzen AI Max+ 395 128GB (Strix Halo) · 74 tok/s at MXFP4
Mac Mini M4 Pro 64GB · 68 tok/s at MXFP4
MacBook M4 Pro 24GB · 68 tok/s at MXFP4
NVIDIA RTX 3060 12GB · 58 tok/s at MXFP4
NVIDIA DGX Spark 128GB · 53 tok/s at MXFP4
MacBook M2 Pro 16GB · won't run

Other models on the CPU-only (Ryzen 9 9950X, 96GB DDR5)

Qwen 3.6/3.8 27B · 3.6 tok/s at Q4_K_M
GLM-5.3 Flash · 14 tok/s at UD-IQ1_S
Gemma 4 26B A4B · 24 tok/s at Q4_K_M
Qwen 3.5/3.6 35B A3B · 33 tok/s at Q4_K_M
Ornith 1.5 35B A3B · 33 tok/s at Q4_K_M
DeepSeek V4 Flash · 15 tok/s at UD-IQ1_M
GPT-OSS 120B · 22 tok/s at MXFP4
Gemma 4 31B · 3.3 tok/s at Q4_K_M
Llama 3.1 8B · 10 tok/s at Q4_K_M
Qwen 3.5 9B · 10 tok/s at Q4_K_M
DeepSeek R1 Distill 14B · 6.6 tok/s at Q4_K_M
Ornith 1.5 9B · 10 tok/s at Q4_K_M
Muse Glimmer 30B · 3.0 tok/s at Q4_K_M
Qwen3 30B A3B · 30 tok/s at Q4_K_M

All models on the CPU-only (Ryzen 9 9950X, 96GB DDR5) · GPT-OSS 20B on all hardware

Estimates for a short prompt on a single device. Measured numbers come from community benchmarks (r/LocalLLaMA, localscore.ai and more); others are derived from similar setups or projected from specs. Open source on GitHub.