GPU5 categories compared

RTX 5070 vs RTX 4080 for LLMs: New Architecture or More VRAM?

The RTX 5070 brings NVIDIA Blackwell architecture at $549 but keeps 12 GB VRAM. The RTX 4080 is last-gen but offers 16 GB VRAM for around $750 used. For LLM inference, VRAM is often the bottleneck — making this a question of architecture speed vs raw memory capacity.

Verdict

NVIDIA RTX 4080 (16 GB)

The RTX 4080 with 16 GB VRAM runs larger models and longer contexts than the RTX 5070 with 12 GB. The RTX 5070 is faster per token on models that fit. For LLM inference specifically, VRAM matters more than architecture generation. Buy the 4080 used if you can find one at a good price.

NVIDIA RTX 5070 (12 GB)

2

wins

Ties

0

draws

NVIDIA RTX 4080 (16 GB)

3

wins

Category-by-Category Breakdown

CategoryNVIDIA RTX 5070 (12 GB)NVIDIA RTX 4080 (16 GB)Winner
VRAM12 GB GDDR716 GB GDDR6XNVIDIA RTX 4080 (16 GB)
Memory Bandwidth448 GB/s (GDDR7)717 GB/sNVIDIA RTX 4080 (16 GB)
Speed on 7B Models~50-60 tok/s~55-65 tok/sNVIDIA RTX 4080 (16 GB)
Price (New)$549 MSRP$750-900 used / discontinued newNVIDIA RTX 5070 (12 GB)
Power Efficiency250W TDP, newer architecture320W TDPNVIDIA RTX 5070 (12 GB)

Detailed Analysis

VRAM

NVIDIA RTX 4080 (16 GB)

4 GB more VRAM means the 4080 can run 14B Q4 models that do not fit on the 5070. For LLMs, VRAM is the most important spec.

NVIDIA RTX 5070 (12 GB)

12 GB GDDR7

NVIDIA RTX 4080 (16 GB)

16 GB GDDR6X

Memory Bandwidth

NVIDIA RTX 4080 (16 GB)

The RTX 4080 has higher effective bandwidth for AI workloads due to its wider memory bus, despite the 5070 using newer GDDR7.

NVIDIA RTX 5070 (12 GB)

448 GB/s (GDDR7)

NVIDIA RTX 4080 (16 GB)

717 GB/s

Speed on 7B Models

NVIDIA RTX 4080 (16 GB)

The 4080 is slightly faster on models that fit in both cards VRAM, thanks to higher memory bandwidth.

NVIDIA RTX 5070 (12 GB)

~50-60 tok/s

NVIDIA RTX 4080 (16 GB)

~55-65 tok/s

Price (New)

NVIDIA RTX 5070 (12 GB)

The 5070 is cheaper new. But used 4080s at $600-700 offer better value for AI workloads.

NVIDIA RTX 5070 (12 GB)

$549 MSRP

NVIDIA RTX 4080 (16 GB)

$750-900 used / discontinued new

Power Efficiency

NVIDIA RTX 5070 (12 GB)

The 5070 uses less power, which matters for always-on inference servers.

NVIDIA RTX 5070 (12 GB)

250W TDP, newer architecture

NVIDIA RTX 4080 (16 GB)

320W TDP

Frequently Asked Questions

Is 12 GB VRAM enough for LLMs in 2025?+
For 7B models, yes. For 14B models, it is too tight. The 12 GB VRAM on RTX 5070 is the biggest limitation for AI use. If you plan to run models larger than 7B, look for 16 GB+ VRAM.
Should I buy RTX 5070 or used RTX 4080 for AI?+
For AI specifically, a used RTX 4080 at $650-700 is the better buy. The extra 4 GB VRAM and higher memory bandwidth matter more for LLM inference than the newer architecture.
Can either card run 30B models?+
Not without offloading to system RAM, which is very slow. For 30B models, you need a 24 GB GPU (RTX 3090, RTX 4090) or Apple Silicon with 48 GB+ unified memory.

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