You can get those numbers with https://codeberg.org/ggz14/radiance-vllm-mxfp4. I also can get it on a single R9700 but the 75 ~ 80 t/s is only peak acceptance of very predictable tokens like coding or json, and averages lower for prose. It's still much faster than regular llama.cpp.
For a single r9700 you have 637 GB/s and for qwen 3.8 27b q4_k_xl the maximum tg/s is 33 before mtp
Now if you meant 4xr9700 tensor parallelism with mtp, 80 tg/s starts to make sense