rtx-5090-benchmarks / reports /gpt-oss-20b-q4-k-m.md
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Benchmark Report: gpt-oss-20b (Q4_K_M)

Date: 2026-06-04
Author: WITCHEER
Platform: NVIDIA GeForce RTX 5090 Benchmark Rig (capsule)


Model

Field Value
Model gpt-oss-20b
Parameters 20.91 B (dense)
Quantization Q4_K_M
File size 10.83 GiB
Engine llama.cpp (CUDA 12.8 (patched))

Hardware

Component Spec
GPU NVIDIA GeForce RTX 5090
CPU AMD Ryzen 5 9600
RAM 64GB DDR5-5600
OS Ubuntu 26.04 LTS
CUDA 12.8 (patched)

Quality Benchmarks

All benchmarks use generative evaluation via llama-server chat completions. Multiple-choice tasks (MMLU, ARC, HellaSwag) use letter extraction instead of loglikelihood scoring -- results are internally consistent for model comparison but absolute scores may differ from logprob-based evaluations by 5-15%.

Summary

Benchmark Score Metric
MMLU 78.56% accuracy
ARC-Challenge 94.62% accuracy
HellaSwag 74.49% accuracy
HumanEval 94.51% pass@1
GSM8K 94.77% exact_match

MMLU Breakdown by Category

Category Score Correct / Total
Stem 89.83% 2,711 / 3,018
Humanities 77.45% 2,456 / 3,171
Social Sciences 84.45% 2,796 / 3,311
Other 67.55% 3,068 / 4,542

Speed Benchmarks

Measured with llama-bench. All layers GPU-offloaded (-ngl 99).

Prompt Processing (tokens/s)

Context Length Speed +/-sigma
128 7,172 73.0
512 16,646 117.8
2048 13,456 36.4
4096 11,684 28.1
8192 9,408 22.7
16384 6,669 4.6

Generation (tokens/s)

Metric Speed +/-sigma
tg128 367.4 0.9

Methodology

Evaluation Framework

Custom generative evaluators built for this rig. All benchmarks run through llama-server's /v1/chat/completions endpoint.

  • Scoring: Generative evaluation (not loglikelihood)
  • Thinking: disabled
  • MCQ scoring: First valid letter extracted from response (A/B/C/D)
  • Sampling: 50% of dataset used
  • Temperature: 0 (deterministic)
  • Max tokens: 2,048
  • GPU offload: All layers (-ngl 99)

Benchmarked by WITCHEER on the RTX 5090 Benchmark Rig. Source: github.com/notwitcheer/llm-bench-rig/blob/main/reports/gpt-oss-20b-q4-k-m.md. Dataset: huggingface.co/datasets/witcheer/rtx-5090-benchmarks/blob/main/reports/gpt-oss-20b-q4-k-m.md.