Qwen3.8 27B
on NVIDIA RTX 3090 · llama.cpp · 229,376 ctx
Summary
User compares llama.cpp built with -DGGML_CUDA_NCCL=OFF against the same build with it ON on 2x RTX 3090.
Setup is the unsloth/Qwen3.8-27B-GGUF UD-Q6_K_XL model at 229k context with an F16 KV cache, tensor split 24,24, and speculative decoding with draft-mtp.
NCCL ON degrades performance: PP 1046.92 vs 958.58 t/s and TG 59.67 vs 54.80 t/s.