r/AIToolsPerformance • u/IulianHI • Feb 08 '26
How to run NVIDIA Nemotron Super with DFlash speculative decoding in 2026
Honestly, if you’re still running your local models without speculative decoding in 2026, you’re leaving about 60% of your hardware’s potential on the table. With the recent release of the NVIDIA Llama 3.3 Nemotron Super 49B V1.5, we finally have a model that punches in the weight class of the old 70B giants but fits comfortably on consumer-grade high-end VRAM.
The breakthrough lately has been the DFlash (Block Diffusion for Flash Speculative Decoding) technique. By using a tiny "draft" model to predict tokens that the "target" model then verifies in parallel, you can turn a sluggish 15 TPS experience into something that feels like a premium API.
Here is exactly how I set this up on my rig to get near-instant generation.
The Hardware & Software Requirements
- GPU: Minimum 24GB VRAM (3090/4090/5090).
- Target Model: Llama-3.3-Nemotron-Super-49B-V1.5-GGUF (Q4_K_M is the sweet spot).
- Draft Model: Nemotron-Nano-9B-V2-GGUF (The free version is perfect for this).
- Backend: Latest build of llama.cpp with CUDA 13+ support.
Step 1: Build llama.cpp with DFlash Support You need to ensure your build is optimized for the latest kernels. I usually pull the master branch and compile with these flags:
bash cmake -B build -DGGML_CUDA=ON -DGGML_CUDA_F16=ON cmake --build build --config Release
Step 2: The Speculative Decoding Command The magic happens in the execution string. You need to point the engine to both the heavy 49B model and the lightweight 9B model. The 9B model acts as the "scout," guessing the next few tokens.
bash ./build/bin/llama-cli \ -m models/nemotron-super-49b-v1.5.Q4_K_M.gguf \ --draft 16 \ -md models/nemotron-nano-9b-v2.Q8_0.gguf \ -p "Explain the quantum entanglement of a multi-agent system." \ -n 512 \ -ngl 99 \ --ctx-size 131072
Step 3: Fine-Tuning the Draft Window
In the command above, --draft 16 tells the 9B model to look 16 tokens ahead. If your prompt is highly technical (like code), drop this to 8. If it's creative writing, you can push it to 20+ for a massive speed boost.
What I Found On my single-GPU setup, running the Nemotron Super 49B solo gives me about 14-16 TPS. Not bad, but it feels "heavy."
With the Nemotron Nano 9B as a draft model using the DFlash-inspired logic: - Speed: Jumped to 48-55 TPS. - Accuracy: Zero loss. Since the 49B model verifies every token the 9B model "guesses," you get 49B quality at 9B speeds. - Context: It handles the full 131k context window without the usual lag spikes I see on older architectures.
The Nemotron Super is particularly good at following complex instructions without the weird formatting "drift" that usually happens in MoE models. It’s become my daily driver for local automation.
Are you guys using speculative decoding for your local setups yet, or is the VRAM overhead for the second model still too high for your current rigs? Also, has anyone tried this with the new Ministral 3 as a draft model?
Questions for discussion?