M3 Ultra 512GB vs NVIDIA RTX 5080 for local LLMs
41 reports on the M3 Ultra 512GB and 31 on the NVIDIA RTX 5080
Which is faster for local LLMs?
Nobody has reported the same model at the same quant on both cards yet, so there's no measured head-to-head. Memory bandwidth, which caps how fast a card can write, is 17% higher on the NVIDIA RTX 5080 (819 GB/s on the M3 Ultra 512GB, 960 on the NVIDIA RTX 5080). The estimates below compare them on the models people run most.
M3 Ultra 512GB
- Memory
- 512GB unified
- Memory bandwidth
- 819 GB/s
- FP16 compute
- 28.4 TFLOPS
- Reports
- 41
NVIDIA RTX 5080
- Memory
- 16GB
- Memory bandwidth
- 960 GB/s
- FP16 compute
- 225 TFLOPS
- Reports
- 31
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.
| Model | M3 Ultra 512GB | NVIDIA RTX 5080 |
|---|---|---|
| Qwen3.8 27B | 8.0 t/sFP16 | 62.6 t/sQ2_K |
| Qwen3.8 125B · 6B active | 13.6 t/sFP16 | doesn't fit at these settings |
| Qwen3.6 35B · 3B active | 28.7 t/sFP16 | 207.0 t/sQ2_K |
| DeepSeek V4 Flash 284B · 13B active | 22.6 t/sQ8_0 | doesn't fit at these settings |
| Qwen3.6 27B | 8.0 t/sFP16 | 62.6 t/sQ2_K |
| Gemma 4 26B · 4B active | 21.5 t/sFP16 | 139.6 t/sQ3_K_S |
Change the context, RAM or model in the calculator: M3 Ultra 512GB · NVIDIA RTX 5080
Every report on each card, with its source: M3 Ultra 512GB · NVIDIA RTX 5080