RTX 3090 vs RTX 5090
The RTX 5090 holds 6 models from our catalog that the RTX 3090 cannot fit at Q4_K_M, and decodes about 1.9× faster on memory bandwidth. Decode speed on a memory-bound workload scales with bandwidth, so that ratio is the number that matters once the model fits at all.
Specs side by side
| Spec | RTX 3090 | RTX 5090 |
|---|---|---|
| VRAM | 24 GB | 32 GB |
| Memory bandwidth | 936 GB/s | 1792 GB/s |
| TDP | 350 W | 575 W |
| Models that fit (Q4_K_M) | 417 of 506 | 423 of 506 |
What the extra VRAM actually buys
6 models in our catalog fit on the RTX 5090 at Q4_K_M but not on the RTX 3090. The largest of them:
Nemotron Super 49B InstructMixtral 8x7BMixtral 8x7B InstructPhi-3.5 MoE 42B (6.6B active) InstructFalcon 40BFalcon 40B Instruct
Largest model each can run
At Q4_K_M the biggest fit in our catalog is Seed-OSS 36B Instruct (22.1 GB) on the RTX 3090, and Nemotron Super 49B Instruct (29.8 GB) on the RTX 5090. Both figures are weights plus runtime overhead; KV cache for your context is extra.
Power and running cost
At 8 hours a day the RTX 3090 draws about 84 kWh a month against 138 kWh for the RTX 5090 — a difference of 54 kWh. Multiply by your own tariff; we do not assume one. Board TDP is the rated figure, not measured draw.
FAQ
RTX 3090 vs RTX 5090: which should I buy for local AI?
The RTX 5090 fits 423 of the 506 models in our catalog at Q4_K_M against 417 for the RTX 3090, and has about 1.9× the memory bandwidth, which is what sets decode speed once a model fits. If the models you run already fit the RTX 3090, the extra spend buys context length and speed, not a new model tier.
Is the RTX 5090 faster than the RTX 3090?
On memory-bound decoding, yes — roughly 1.9× the throughput, since token generation scales with memory bandwidth (1792 GB/s vs 936 GB/s). This is an upper bound from bandwidth alone, not a measured benchmark.
How much more VRAM does the RTX 5090 have?
8 GB more (32 GB vs 24 GB). That difference lets it hold 6 additional models from our catalog at Q4_K_M.
Need a third card in the mix? The interactive compare tool lines up any three. To size KV cache for your context length, use the GPU Memory Calculator.
Related matchups
Other head-to-heads involving these cards:
RTX 4090 vs RTX 5090RTX 3090 vs RTX 4090RTX 5090 vs RTX A6000RTX 5090 vs H100 80GBRTX 5090 vs L40S
New to sizing? What VRAM is and why bandwidth sets decode speed cover the basics, and quantization explains the formats in the table above. Common mistakes when sizing VRAM lists the traps.