GPU ·Published 2026-04-15 · Updated 2026-06-04

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

The RTX 5070 brings NVIDIA Blackwell architecture but keeps 12 GB VRAM. The RTX 4080 is last-gen but offers 16 GB VRAM and a used 4080 often costs less than a new 5080. For LLM inference, VRAM is often the bottleneck, making this a question of architecture speed vs raw memory capacity.

NVIDIA RTX 5070 (12 GB)
2wins
Ties
1draws
NVIDIA RTX 4080 (16 GB)
2wins
Categories compared
5

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. Bandwidth is close between them (717 vs 672 GB/s, about 7%), so token speed is close too. For LLM inference specifically, VRAM is the deciding factor. Buy the 4080 used if you can find one at a good price.

Table 1

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 Bandwidth672 GB/s (GDDR7)717 GB/sNVIDIA RTX 4080 (16 GB)
Speed on 8B Models~98 tok/s (est.)Within a few percent of the 5070Tie
Price (New)Lower (new)Higher (used or discontinued new)NVIDIA 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 still has slightly more bandwidth (717 vs 672 GB/s), but GDDR7 closes most of the gap: the difference is only about 7%, not the wide margin a narrower memory bus would suggest.

NVIDIA RTX 5070 (12 GB)
672 GB/s (GDDR7)
NVIDIA RTX 4080 (16 GB)
717 GB/s

Speed on 8B Models

Tie

The 4080 has about 7% more bandwidth, but GDDR7 and Blackwell make up most of that in ModelFit estimates, so the two land close together on an 8B model that fits both cards. The 5070 is estimated at about 98 tok/s.

NVIDIA RTX 5070 (12 GB)
~98 tok/s (est.)
NVIDIA RTX 4080 (16 GB)
Within a few percent of the 5070

Price (New)

NVIDIA RTX 5070 (12 GB)

The 5070 is cheaper new. A used 4080 can offer better value for AI workloads.

NVIDIA RTX 5070 (12 GB)
Lower (new)
NVIDIA RTX 4080 (16 GB)
Higher (used or 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 can be the better buy when it costs less than a new RTX 5070. The extra 4 GB VRAM matters more for LLM inference than the newer architecture, since speed is close between the two.
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.

Where to buy the RTX 5070

View the RTX 5070 12GB on Amazon

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Where to buy the RTX 4080

Search RTX 4080 listings on Amazon
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