Radeon RX 7900 XTX vs. RTX 4090: which GPU for local AI?
Focused comparison Local LLM : we're looking at what really matters for running models—VRAM above all, then generation speed and price. Purchase verdict at the end.
Updated on 09/10/2026
Comparison at a glance
| Criterion | Radeon RX 7900 XTX | RTX 4090 |
|---|---|---|
| Memory | 24 GB VRAM | 24 GB VRAM |
| Brand | AMD | NVIDIA |
| Compatible models (Q4) | 178 models in the catalog | 178 models in the catalog |
| Largest model (Q4) | Salamandra 40B Instruct (40B) | Salamandra 40B Instruct (40B) |
Which one should you choose to run an LLM?
Golden rule: with the same budget, always choose the GPU with the most VRAM. A model that exceeds the VRAM limit collapses in speed (CPU offloading). VRAM determines the size of the model; computing power mainly dictates the Speed.
Where to buy (up-to-date pricing and stock)
Alternative purchase: GMKtec EVO-X2 64 GB / 1 TB (Ryzen AI Max+ 395). A mini PC is a complete machine, not a replacement board; check memory and software compatibility.
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Frequently asked questions
Radeon RX 7900 XTX or RTX 4090 for running an LLM locally?
For local use, the VRAM prime. The Radeon RX 7900 XTX (24 GB) runs larger models than the RTX 4090 (24 GB).
What is the largest model the Radeon RX 7900 XTX can run?
Up to Salamandra 40B Instruct (40B) in Q4 quantization, with its 24 GB.
Should you buy used?
For LLMs, a used GPU with more VRAM often beats a newer card with less memory. Check its condition and warranty.