GPT-OSS 20B (MoE) at FP8 (E4M3) needs 20.9 GB for its weights and 22.6 GB in total at 8K context with 8 concurrent users. That means it fits on a single RTX PRO 6000 Blackwell 96GB. Every figure is computed by tokcalc's open-source capacity model.
| GPUs | Total VRAM | VRAM needed | Decode tok/s | Aggregate tok/s | TTFT | Cost / 1M tok | Fits? |
|---|---|---|---|---|---|---|---|
| 1× RTX | 96 GB | 22.6 GB | 485.3 | 5824 | 975.8 ms | $0.0715 | ✓ |
| 2× RTX | 192 GB | 22.6 GB | 825.1 | 19802 | 503.1 ms | $0.0421 | ✓ |
| 4× RTX | 384 GB | 22.6 GB | 1650 | 79206 | 266.5 ms | $0.0210 | ✓ |
| 8× RTX | 768 GB | 22.6 GB | 3300 | 316826 | 148.3 ms | $0.0105 | ✓ |
| Context | Concurrent users | KV per request | Fits? |
|---|---|---|---|
| 4K | 723 | 206.2 MB | ✓ fits |
| 8K | 367 | 412.3 MB | ✓ fits |
| 33K | 92 | 1.61 GB | ✓ fits |
| 66K | 46 | 3.22 GB | ✓ fits |
| 131K | 23 | 6.44 GB | ✓ fits |
| GPU | GPUs | Aggregate tok/s | Cost / 1M tok |
|---|---|---|---|
| RTX 5090 32GB | 1× | 5824 | $0.0238 |
| RTX 3090 24GB | 1× | 2472 | $0.0281 |
| RTX 4090 24GB | 1× | 3276 | $0.0339 |
| AMD MI300X 192GB | 1× | 17225 | $0.0403 |
| V100 SXM2 32GB | 1× | 2925 | $0.0475 |
| A100 40GB SXM4 | 1× | 5038 | $0.0496 |
Yes. GPT-OSS 20B (MoE) at FP8 (E4M3) needs 22.6 GB including the KV cache, and RTX PRO 6000 Blackwell 96GB has 96 GB — so it fits on a single GPU.
485.3 tokens/sec per stream and 5824 tok/s aggregate with continuous batching at 8 concurrent users. Time to first token is 975.8 ms, and inter-token latency is 2.1 ms.
$0.0715 per 1M output tokens at 1× RTX PRO 6000 Blackwell 96GB ($1.50/hr). That is the marginal hardware cost — add idle capacity, ops, and egress for the real figure.
20.9 GB for the weights at FP8 (E4M3), plus 1.6 GB of KV cache for 8 concurrent requests at 8K context — 22.6 GB total. Every extra concurrent user at long context costs more, so leave headroom.
It works. Compare $0.0715 per 1M tokens against the alternatives below — the cheapest option that fits the same workload is 4× RTX 3080 10GB at $0.006615, and the fastest is 1× Cerebras CS-3 (WSE-3) at 65000 tok/s.
Same formulas, your context length, concurrency, and quantisation.