Local AI Advisor

Can Desktop PC · GeForce RTX 5070 · 32 GB RAM run gpt-oss-20b?

12 GB VRAM + 32 GB RAM · 672 GB/s memory bandwidth · gpt-oss-20b has 20.9B parameters (3.6B active per token).

Short answer

It loads, but it's borderline even for chat.

Best quantization for chat: MXFP4 (11 GB of weights) on Ollama. Generation: 60–100 tok/s, leaving about 0.0 GB free for your other apps.

How it rates for each workload

Same model and machine, different jobs. Agents and long documents send far bigger prompts than chat, so they need much more speed and memory.

WorkloadVerdictQuantGenerationFirst replyContext
Chatwith Open WebUIBorderlineMXFP460–100 tok/sunder 1 s8KDetails
Coding questionswith ContinueBorderlineMXFP450–85 tok/s≈2 s16KDetails
Coding in a repositorywith AiderBorderlineMXFP440–70 tok/s≈7 s32KDetails
Agentic codingwith OpenCodeBorderlineMXFP440–65 tok/s≈10 s32KDetails
Long documents (64K)with Open WebUIBorderlineMXFP425–40 tok/s≈35 s64KDetails

Speeds are bandwidth-based estimates; no direct benchmark exists for this pair. “First reply” is the time to read the workload’s opening prompt. How we calculate

Get it running

Copy-paste commands for the MXFP4 build with a 8K context. Ollama and llama.cpp download the file straight from Hugging Face.

ollama run hf.co/unsloth/gpt-oss-20b-GGUF:F16

Downloads 13.79 GB (F16). Ollama's default context is small: set OLLAMA_CONTEXT_LENGTH=8192 before `ollama serve` for long prompts.

Different tool, context size or workload?

These pages use typical settings. The full check models your exact setup.