gpt-oss-20b strains RTX 5070, 12GB

Hot take: yes, it can probably run, but not in the clean, all-on-GPU way a beginner usually hopes for. Your 12GB card is below the model’s comfortable floor, so the real question is less “will it start?” and more “will it feel fast enough to enjoy?”

• –OpenAI says gpt-oss-20b is designed for local inference and can run with as little as 16GB of memory; Ollama ships it directly.
• –A 12GB RTX 5070 is short of that target, so you should expect heavy quantization, reduced context, or spillover into system RAM.
• –Your 32GB of RAM helps, and the i5-12600K is plenty for offload-heavy setups, but RAM does not replace VRAM for speed.
• –The subreddit replies lean toward smaller dense models like Qwen 3.5 9B for a better beginner experience on 12GB cards.
• –If your goal is experimentation, this is viable; if your goal is smooth daily use, a smaller model will probably feel much better.