RTX 5090 vs RTX 4090 for Local LLMs
RTX 5090 vs RTX 4090 for local LLMs: 32 GB GDDR7 vs 24 GB GDDR6X, 1,792 vs 1,008 GB/s bandwidth. Which is better for your inference workload and budget?
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GPU Comparison
GeForce RTX 5090 vs GeForce RTX 4090 for Local LLMs
The RTX 5090 offers 32 GB GDDR7 at 1,792 GB/s — enough to run any consumer-relevant model. The used 4090 offers 24 GB GDDR6X at 1,008 GB/s at half the price. Which should you buy for local LLM inference?
01 / Specifications
Spec by Spec
02 / Model Support
32 GB vs 24 GB: What You Can Run
The single biggest difference between these cards is VRAM. 32 GB opens up 70B models at Q4 without offloading. 24 GB covers everything below that tier comfortably.
GeForce RTX 5090 — 32 GB
Llama 3.1 70B (Q4_K_M)
~38 GB — Fits entirely on GPU
Mixtral 8x7B (Q4_K_M)
~14 GB — Room to spare
Qwen 2.5 32B (Q4_K_M)
~18 GB — Comfortable
Command R 35B (Q4_K_M)
~20 GB — Comfortable
GeForce RTX 4090 — 24 GB
Llama 3.1 70B (Q4_K_M)
~38 GB — Needs ~14 GB offload
Mixtral 8x7B (Q4_K_M)
~14 GB — Fits well
Qwen 2.5 32B (Q4_K_M)
~18 GB — Fits well
Command R 35B (Q4_K_M)
~20 GB — Fits well
03 / Strengths & Weaknesses
Pros and Cons
GeForce RTX 5090 — Strengths
Strengths
- 32 GB VRAM fits most useful models at usable quantizations
- 1,792 GB/s bandwidth — fastest consumer GPU for inference
- Full CUDA ecosystem support with no configuration headaches
- FP8 and Flash Attention 2 support for faster inference
Weaknesses
- 575 W TDP demands a 1,000 W PSU and strong cooling
- Most expensive consumer GPU on the market
- Overkill if you only run 7B-13B models
GeForce RTX 4090 — Strengths
Strengths
- 1,008 GB/s bandwidth — faster than the new RTX 5080
- 24 GB VRAM opens up 70B-class models
- Full CUDA + FP8 + Flash Attention support
- Significant discount over buying new
Weaknesses
- No warranty on used cards
- 450 W TDP needs a strong PSU and good cooling
- Risk of degraded hardware from mining or heavy use
04 / Verdict
The Bottom Line
Best for Most
GeForce RTX 5090
Buy the RTX 5090 if you regularly run Llama 3.1 70B at Q4 and want it entirely on GPU without offloading. The 32 GB VRAM is the only consumer option that achieves this. You pay $800 more than a used 4090, but you get VRAM headroom, 78% more bandwidth, and a full warranty.
Best for Value
GeForce RTX 4090
Buy the used RTX 4090 if your models fit in 24 GB (Mixtral 8x7B, Qwen 32B, Command R 35B at Q4). The 1,008 GB/s bandwidth is still faster than the new RTX 5080. At ~$1,200 used, it is the best value in high-performance LLM hardware.
For the full lineup at every budget, see our Best GPU for Local LLMs guide.
05 / Related
More Comparisons
Frequently Asked Questions
Is the RTX 5090 worth the premium over a used RTX 4090 for LLMs?
Does the RTX 5090 generate tokens faster than the RTX 4090?
Can the RTX 4090 run Llama 70B?
Is FP8 support different between the two?
Looking for specific GPU recommendations? Our main guide covers every budget and VRAM tier.
Best GPU for Local LLMs →