M3 Max 128GB vs M3 Ultra 256GB for local LLMs
6 reports on the M3 Max 128GB and 15 on the M3 Ultra 256GB
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 2.0x higher on the M3 Ultra 256GB (410 GB/s on the M3 Max 128GB, 819 on the M3 Ultra 256GB). The estimates below compare them on the models people run most.
M3 Max 128GB
- Memory
- 128GB unified
- Memory bandwidth
- 410 GB/s
- FP16 compute
- 14.2 TFLOPS
- Reports
- 6
M3 Ultra 256GB
- Memory
- 256GB unified
- Memory bandwidth
- 819 GB/s
- FP16 compute
- 28.4 TFLOPS
- Reports
- 15
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 Max 128GB | M3 Ultra 256GB |
|---|---|---|
| Qwen3.8 27B | 5.3 t/sFP16 | 8.0 t/sFP16 |
| Qwen3.8 125B · 6B active | 24.3 t/sQ5_K_S | 27.3 t/sQ8_0 |
| Qwen3.6 35B · 3B active | 16.8 t/sFP16 | 28.7 t/sFP16 |
| DeepSeek V4 Flash 284B · 13B active | 38.2 t/sQ2_K | 36.0 t/sQ4_K_M |
| Qwen3.6 27B | 5.3 t/sFP16 | 8.0 t/sFP16 |
| Gemma 4 26B · 4B active | 14.4 t/sFP16 | 21.5 t/sFP16 |
Change the context, RAM or model in the calculator: M3 Max 128GB · M3 Ultra 256GB
Every report on each card, with its source: M3 Max 128GB · M3 Ultra 256GB