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GPU · 7 min read

RTX 5090 vs RTX 4090 for local AI: which to choose in 2026?

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Damien · LocalIA
Published 2026-06-05

The calm matchup from the angle that matters: which models run, at what throughput, for what price. VRAM (32 vs 24 GB), GDDR7 bandwidth, a models table, and the verdict by profile.

For local AI in 2026, the RTX 5090 (32 GB) beats the RTX 4090 (24 GB) on the one metric that matters most: VRAM. Those 8 extra gigabytes unlock models the 4090 cannot hold, such as Llama 70B in Q3. But if your models already fit in 24 GB, a used RTX 4090 remains the best value per euro.

Key numbers

VRAM24 GB GDDR6X32 GB GDDR7
Memory bandwidth~1,008 GB/s~1,792 GB/s
TDP450 W575 W
Indicative new price 2026~EUR 1,600-1,900~EUR 2,200-2,700

The number that changes everything

The RTX 5090 has about 78% more memory bandwidth thanks to GDDR7. LLM inference is memory-bound: tokens per second depend far more on bandwidth than on raw compute. That, plus the 8 extra gigabytes, is where the 5090 pulls ahead.

Which models run on each

Mistral 7B / Llama 8BFP16 yesFP16 yes
Qwen 32B / Gemma 31BQ4 yes, Q5 tightQ5 yes, Q6 yes
Llama 3.3 70B / Qwen 72BQ3 very tightQ3 yes (Q4 out of reach)
Llama 4 Scout 109B (MoE)Too bigNeeds two cards

Throughput and value

On a model that fits both cards, the RTX 5090 delivers roughly 40 to 70% more tokens per second. The gap is most visible on multi-request use and long contexts.

The used RTX 4090 (around EUR 1,100-1,400) stays the best value if your models fit in 24 GB, you run solo or in a small team, and you do not need the 70B tier. The 5090 is worth it for 70B on a single card, long context, or serving several users.

  • Solo dev, models up to 32B: used RTX 4090 — unbeatable value.
  • You want Llama 70B on one card: RTX 5090 — the 4090 cannot follow.
  • Multi-user or long context: RTX 5090 — the GDDR7 bandwidth pays off.
  • 100B+ models: multi-GPU (NVLink) — neither card alone.
Enter your card and target model in the LocalIA GPU to LLM calculator: it tells you whether it fits, at which quantization, with estimated VRAM and throughput, across 200+ GPUs. Free, no signup. LocalIA is an independent resource and sells nothing.

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Frequently asked questions

RTX 5090 or RTX 4090 for local AI?+
The RTX 5090 (32 GB) unlocks models the 4090 (24 GB) cannot hold, such as Llama 70B in Q3, and delivers ~40-70% more tokens/second thanks to GDDR7. If your models already fit in 24 GB, a used RTX 4090 stays the best value for money.
What is the VRAM difference between RTX 4090 and RTX 5090?+
24 GB (GDDR6X) on the 4090 versus 32 GB (GDDR7) on the 5090. Those 8 extra GB, plus ~78% higher memory bandwidth, are the 5090's real advantages for LLM inference (which is memory-bound).
Can you run Llama 70B on an RTX 4090?+
Just barely, in Q3 and with little context — it is tight on 24 GB. The RTX 5090 (32 GB) holds Llama 3.3 70B in Q3 more comfortably. For Q4/Q5 you need multi-GPU.
Are two RTX 4090s better than one RTX 5090?+
2x RTX 4090 = 48 GB combined, more than the 5090, but without NVLink the multi-GPU link goes over PCIe, slower on very large models. For a 70B, a single RTX 5090 is often smoother than a pair of 4090s on PCIe.
Is the RTX 5090 worth its price for local AI?+
Yes if you want Llama 70B on a single card, lots of context, or more throughput to serve several users. No if your models fit in 24 GB: a used RTX 4090 then stays unbeatable on value.
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