NVIDIA RTX 3090 vs AMD Radeon RX 7900 XTX

Analysis

The RTX 3090 and Radeon RX 7900 XTX share the exact same 24GB VRAM ceiling on two different vendors' silicon, which makes this one of the cleanest NVIDIA-vs-AMD comparisons on this site: neither card has an obvious capacity advantage over the other, so the real differences come down to a small bandwidth edge for AMD and a much larger ecosystem gap between CUDA and ROCm.

With identical 24GB budgets, this site's calculator fits the same 52 of the 94 tracked models natively on either card at 8k context. The RX 7900 XTX's 960 GB/s edges out the RTX 3090's 936 GB/s by 2.6%, and that shows up as a small, consistent speed edge for AMD on everything both cards fit: Llama 3.1 8B at Q4_K_M runs 104.9 tok/s on the RX 7900 XTX versus 102.3 tok/s on the RTX 3090, Qwen 3.6 27B at Q4_K_M runs 36.7 versus 35.8 tok/s, and Qwen3 32B at Q4_K_M, which needs CPU offload on both cards at that quant (23.88 GB against roughly 22.8 GB of usable VRAM), still runs 29.3 versus 28.5 tok/s. None of those gaps are decisive on their own, a couple of percent either way. The bigger difference is software: the RTX 3090 runs on CUDA, a mature target every major inference tool (llama.cpp, Ollama, vLLM, TensorRT-LLM) has had years to optimize, while the RX 7900 XTX needs ROCm, which is Linux-only for GPU acceleration and requires a llama.cpp build compiled with ROCm support; Windows users fall back to the slower Vulkan backend instead. The RTX 3090 also keeps one option the RX 7900 XTX doesn't: a working NVLink bridge for pooling two cards into a 48GB address space, reaching 70B-class models the way this site's own RTX 3090 page shows in detail. AMD has no equivalent consumer bridge on RDNA 3, so a multi-GPU RX 7900 XTX setup for 70B-class models depends entirely on ROCm's own peer-to-peer and layer-split support, which is real but far less commonly documented for local inference than llama.cpp's NVIDIA-first multi-GPU tooling.

Bottom line: On raw hardware, this is close to a wash: AMD's small bandwidth edge buys a couple of percent more tokens per second on anything both cards fit, and both share the identical 24GB ceiling. The decision comes down to software maturity and what you plan to do beyond a single card: pick the RTX 3090 for the more mature CUDA ecosystem, broader tool support, and the option to pool two cards over NVLink for 70B-class models later. Pick the RX 7900 XTX if you're already committed to a Linux ROCm workflow, want the modest speed edge on single-card use, or can find it meaningfully cheaper than a comparable RTX 3090 on the used market.