NVIDIA RTX 3080 20GB vs NVIDIA RTX 4090 for local LLMs
13 reports on the NVIDIA RTX 3080 20GB and 55 on the NVIDIA RTX 4090
Which is faster for local LLMs?
On Qwen3.8 27B at 4-bit, the NVIDIA RTX 3080 20GB has 25.7 generation tokens/s (2 runs); prompt processing 997.0 tokens/s (one run); the NVIDIA RTX 4090 has 40.0 generation tokens/s (3 runs); prompt processing 1949.3 tokens/s (2 runs). Those are community reports whose engines and settings differ, so the gap is a rough sign, not a controlled measure of the two cards. Memory bandwidth, which caps how fast a card can write, is 33% higher on the NVIDIA RTX 4090 (760 GB/s on the NVIDIA RTX 3080 20GB, 1,008 on the NVIDIA RTX 4090).
- Memory
- 20GB
- Memory bandwidth
- 760 GB/s
- FP16 compute
- 119 TFLOPS
- Reports
- 13
- Memory
- 24GB
- Memory bandwidth
- 1,008 GB/s
- FP16 compute
- 330 TFLOPS
- Reports
- 55
Measured on both
Generation and prompt processing speeds from plain runs (one device, one request, no speculative decoding, the whole model in the device's memory) of the same model size at the same bit class. Each side shows the engines and reported context behind its median. Context can mean a configured window or prompt depth, so these are community comparisons with differing settings. How to read these
| Model | NVIDIA RTX 3080 20GB | NVIDIA RTX 4090 |
|---|---|---|
| Qwen3.8 27B4-bit | 25.72 runsPP 997.0 (one run)llama.cpp, 1 not stated96K context, 1 not stated | 40.03 runsPP 1949.3 (2 runs)llama.cpp8K to 194K context |
Estimated by the calculator
The quant the calculator recommends for each card and its estimated speed at a 32,768-token context with 32 GB of system RAM, from memory bandwidth and the model's shape. Where a model was also measured above, the measurement wins.
| Model | NVIDIA RTX 3080 20GB | NVIDIA RTX 4090 |
|---|---|---|
| Qwen3.8 27B | 35.4 t/sQ3_K_M | 36.5 t/sQ4_K_M |
| Qwen3.8 125B · 6B active | 19.1 t/sQ2_K, experts in RAM | 19.6 t/sQ2_K, experts in RAM |
| Qwen3.6 35B · 3B active | 140.5 t/sQ3_K_S | 129.3 t/sQ4_K_S |
| DeepSeek V4 Flash 284B · 13B active | doesn't fit at these settings | doesn't fit at these settings |
| Qwen3.6 27B | 35.4 t/sQ3_K_M | 36.5 t/sQ4_K_M |
| Gemma 4 26B · 4B active | 79.7 t/sQ4_K_S | 82.3 t/sQ5_K_S |
| DeepSeek V4.1 Flash 552B · 16B active | doesn't fit at these settings | doesn't fit at these settings |
Change the context, RAM or model in the calculator: NVIDIA RTX 3080 20GB · NVIDIA RTX 4090
Every report on each card, with its source: NVIDIA RTX 3080 20GB · NVIDIA RTX 4090