Step 3.5 Flash — Hardware Requirements & GPU Compatibility
Chat
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.
83.6K downloads
714 likesSpecifications
- Publisher
- stepfun-ai
- Parameters
- 199.4B
- Architecture
- Step3p5ForCausalLM
- Context Length
- 262,144 tokens
- Vocabulary Size
- 128,896
- Release Date
- 2026-03-09
- 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 |
|---|---|---|---|---|---|
| IQ4_XS | 4.30 | 117.9 GB | — | 107.17 GB | Importance-weighted 4-bit, compact |
Which GPUs Can Run Step 3.5 Flash?
IQ4_XS · 117.9 GBStep 3.5 Flash (IQ4_XS) requires 117.9 GB of VRAM to load the model weights. For comfortable inference with headroom for KV cache and system overhead, 154+ GB is recommended. No single GPU has enough memory — multi-GPU or cluster setups are needed.
Which Devices Can Run Step 3.5 Flash?
IQ4_XS · 117.9 GB5 devices with unified memory can run Step 3.5 Flash, including NVIDIA DGX H100, NVIDIA DGX A100 640GB, Mac Studio M4 Max (128 GB).
Runs great
— Plenty of headroom
Decent
— Enough memory, may be tightRelated Models
Frequently Asked Questions
- How much VRAM does Step 3.5 Flash need?
Step 3.5 Flash requires 117.9 GB of VRAM at IQ4_XS.
VRAM = Weights + KV Cache + Overhead
Weights = 199.4B × 4.3 bits ÷ 8 = 107.2 GB
KV Cache + Overhead ≈ 10.7 GB (at 2K context + ~0.3 GB framework)
VRAM usage by quantization
IQ4_XS117.9 GB- Can NVIDIA GeForce RTX 5090 run Step 3.5 Flash?
No — Step 3.5 Flash requires at least 117.9 GB at IQ4_XS, which exceeds the NVIDIA GeForce RTX 5090's 32 GB of VRAM.
- Can I run Step 3.5 Flash on a Mac?
Step 3.5 Flash requires at least 117.9 GB at IQ4_XS, 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 IQ4_XS quantization it needs 117.9 GB of VRAM. Popular tools include Ollama, LM Studio, and llama.cpp.
- How fast is Step 3.5 Flash?
At IQ4_XS, Step 3.5 Flash can reach ~25 tok/s on AMD Instinct MI300X. Speed depends mainly on GPU memory bandwidth. Real-world results typically within ±20%.
tok/s = (bandwidth GB/s ÷ model GB) × efficiency
Example: AMD Instinct MI300X → 5300 ÷ 117.9 × 0.55 = ~25 tok/s
Estimated speed at IQ4_XS (117.9 GB)
~25 tok/s~15 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 IQ4_XS, the download is about 107.17 GB.
- Which GPUs can run Step 3.5 Flash?
No single consumer GPU has enough VRAM to run Step 3.5 Flash at IQ4_XS (117.9 GB). Multi-GPU or professional hardware is required.
- Which devices can run Step 3.5 Flash?
5 devices with unified memory can run Step 3.5 Flash at IQ4_XS (117.9 GB), including Mac Pro M2 Ultra (192 GB), Mac Studio M2 Ultra (192 GB), Mac Studio M4 Max (128 GB), NVIDIA DGX A100 640GB. Apple Silicon Macs use unified memory shared between CPU and GPU, making them well-suited for local LLM inference.