Step 3.5 Flash — Hardware Requirements & GPU Compatibility
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Step 3.5 Flash is an efficient mixture-of-experts model from StepFun AI, a Chinese AI startup, featuring roughly 199 billion total parameters. The Flash designation signals its focus on speed and low-latency inference, making it well-suited for interactive applications despite its large total parameter count. Running it locally requires a multi-GPU setup, but its MoE architecture means only a portion of the model activates per token, delivering strong multilingual performance with better throughput than a comparably sized dense model.
358.2K downloads
821 likesSpecifications
- Publisher
- stepfun-ai
- Parameters
- 199.4B
- Architecture
- Step3p5ForCausalLM
- Context Length
- 262,144 tokens
- Vocabulary Size
- 128,896
- Release Date
- 2026-02-01
- License
- Apache 2.0
Get Started
HuggingFace
How Much VRAM Does Step 3.5 Flash Need?
Select a quantization to see compatible GPUs below.
| Quantization | Bits | VRAM | + Context | File Size | Quality |
|---|---|---|---|---|---|
| Q2_K | 3.40 | 93.2 GB | — | 84.74 GB | 2-bit quantization with K-quant improvements |
| Q3_K_S | 3.50 | 96.0 GB | — | 87.23 GB | 3-bit small quantization |
| Q3_K_M | 3.90 | 106.9 GB | — | 97.20 GB | 3-bit medium quantization |
| Q4_K_M | 4.80 | 131.6 GB | — | 119.63 GB | 4-bit medium quantization — most popular sweet spot |
| Q5_K_M | 5.70 | 156.3 GB | — | 142.06 GB | 5-bit medium quantization — good quality/size tradeoff |
| Q6_K | 6.60 | 180.9 GB | — | 164.49 GB | 6-bit quantization, very good quality |
| Q8_0 | 8.00 | 219.3 GB | — | 199.38 GB | 8-bit quantization, near-lossless |
est.= calculated VRAM estimate; no published GGUF file found for that quantization yet. Other rows are verified against real community uploads.
Which GPUs Can Run Step 3.5 Flash?
Q4_K_M · 131.6 GBStep 3.5 Flash (Q4_K_M) requires 131.6 GB of VRAM to load the model weights. For comfortable inference with headroom for KV cache and system overhead, 172+ GB is recommended. No single GPU has enough memory — multi-GPU or cluster setups are needed.
Which Devices Can Run Step 3.5 Flash?
Q4_K_M · 131.6 GB6 devices with unified memory can run Step 3.5 Flash, including NVIDIA DGX H100, NVIDIA DGX A100 640GB, Mac Studio (M3 Ultra, 256GB).
Runs great
— Plenty of headroom
Decent
— Enough memory, may be tightWhere to Download Step 3.5 Flash
Community quantizations of this model — GGUF for llama.cpp, Ollama, and LM Studio, plus AWQ/MLX variants where available.
Related Models
Frequently Asked Questions
- How much VRAM does Step 3.5 Flash need?
Step 3.5 Flash requires 131.6 GB of VRAM at Q4_K_M, or 438.6 GB at BF16.
VRAM = Weights + KV Cache + Overhead
Weights = 199.4B × 4.8 bits ÷ 8 = 119.6 GB
KV Cache + Overhead ≈ 12 GB (at 2K context + ~0.3 GB framework)
VRAM usage by quantization
Q4_K_M131.6 GB- Can NVIDIA GeForce RTX 5090 run Step 3.5 Flash?
No — Step 3.5 Flash requires at least 68.5 GB at IQ2_S, which exceeds the NVIDIA GeForce RTX 5090's 32 GB of VRAM.
- What's the best quantization for Step 3.5 Flash?
For Step 3.5 Flash, Q4_K_M (131.6 GB) offers the best balance of quality and VRAM usage. Q5_K_S (150.8 GB) provides better quality if you have the VRAM. The smallest option is IQ2_S at 68.5 GB.
VRAM requirement by quantization
IQ2_S68.5 GBQ3_K_S96.0 GBQ4_K_S123.4 GBQ4_K_M ★131.6 GBQ5_K_M156.3 GBBF16438.6 GB★ Recommended — best balance of quality and VRAM usage.
- Can I run Step 3.5 Flash on a Mac?
Step 3.5 Flash requires at least 68.5 GB at IQ2_S, which exceeds the unified memory of most consumer Macs. You would need a Mac Studio or Mac Pro with a high-memory configuration.
- Can I run Step 3.5 Flash locally?
Yes — Step 3.5 Flash can run locally on consumer hardware. At Q4_K_M quantization it needs 131.6 GB of VRAM. Popular tools include Ollama, LM Studio, and llama.cpp.
- How fast is Step 3.5 Flash?
At Q4_K_M, Step 3.5 Flash can reach ~33 tok/s on AMD Instinct MI350X. Speed depends mainly on GPU memory bandwidth. Real-world results typically within ±20%.
tok/s = (bandwidth GB/s ÷ model GB) × efficiency
Example: NVIDIA B200 → 8000 ÷ 131.6 × 0.65 = ~40 tok/s
Estimated speed at Q4_K_M (131.6 GB)
~40 tok/s~40 tok/s~33 tok/sReal-world results typically within ±20%. Speed depends on batch size, quantization kernel, and software stack.
- What's the download size of Step 3.5 Flash?
At Q4_K_M, the download is about 119.63 GB. The full-precision BF16 version is 398.77 GB. The smallest option (IQ2_S) is 62.31 GB.
- Which GPUs can run Step 3.5 Flash?
No single consumer GPU has enough VRAM to run Step 3.5 Flash at Q4_K_M (131.6 GB). Multi-GPU or professional hardware is required.
- Which devices can run Step 3.5 Flash?
6 devices with unified memory can run Step 3.5 Flash at Q4_K_M (131.6 GB), including Mac Pro M2 Ultra (192 GB), Mac Studio (M3 Ultra, 256GB), Mac Studio (M3 Ultra, 512GB), Mac Studio M2 Ultra (192 GB). Apple Silicon Macs use unified memory shared between CPU and GPU, making them well-suited for local LLM inference.