Short answer
gpt-oss-120b typically requires a workstation/server GPU with ~60–80 GB of VRAM for single‑GPU local inference (80 GB is the common “safe” target). Multi‑GPU setups (model‑/tensor‑parallelism) can reduce per‑GPU VRAM requirements but add complexity. (ollama.com) Recommended hardware (concise)
GPU VRAM: 80 GB (single‑GPU recommended). LM Studio notes “best with ≥60 GB VRAM” but most vendor docs and deploy guides target an 80 GB card (NVIDIA A100/H100 class) for the full 120B. Multi‑GPU with NVLink/NVSwitch can be used instead of one 80 GB card. (xlxm.cn) System RAM: 64–128 GB (128 GB recommended if you’ll run other services, caching, or multi‑GPU setups). Some production guides recommend 128 GB+ for comfort. (gptoss.net) CPU: Many cores for throughput; a modern server/workstation CPU (16+ cores recommended; 32+ cores for heavy multi‑client/production). High PCIe bandwidth and many PCIe lanes are helpful when attaching big GPUs. (gptoss.net) Storage: NVMe SSD (fast) — plan for ~100 GB to store th