M1 Ultra 128GB vs AMD RX 7900 XTX for local LLMs
3 reports on the M1 Ultra 128GB and 32 on the AMD RX 7900 XTX
Which is faster for local LLMs?
On Qwen3.8 27B at 4-bit, the M1 Ultra 128GB runs at 25.1 tokens per second (one run) and the AMD RX 7900 XTX at 48.0 (3 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 17% higher on the AMD RX 7900 XTX (819 GB/s on the M1 Ultra 128GB, 960 on the AMD RX 7900 XTX).
- Memory
- 128GB unified
- Memory bandwidth
- 819 GB/s
- FP16 compute
- 21 TFLOPS
- Reports
- 3
- Memory
- 24GB
- Memory bandwidth
- 960 GB/s
- FP16 compute
- 123 TFLOPS
- Reports
- 32
Measured on both
Median tokens per second 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 quant level. Engines and context lengths can still differ between the runs. How to read these
| Model | M1 Ultra 128GB | AMD RX 7900 XTX |
|---|---|---|
| Qwen3.8 27B4-bit | 25.1one run | 48.03 runs |
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 | M1 Ultra 128GB | AMD RX 7900 XTX |
|---|---|---|
| Qwen3.8 27B | 7.5 t/sFP16 | 34.8 t/sQ4_K_M |
| Qwen3.8 125B · 6B active | 34.0 t/sQ5_K_S | 19.5 t/sQ2_K, experts in RAM |
| DeepSeek V4 Flash 284B · 13B active | 53.5 t/sQ2_K | doesn't fit at these settings |
| Qwen3.6 35B · 3B active | 23.5 t/sFP16 | 123.2 t/sQ4_K_S |
| Qwen3.6 27B | 7.5 t/sFP16 | 34.8 t/sQ4_K_M |
| GLM-5.3 320B · 18B active | doesn't fit at these settings | doesn't fit at these settings |
| Gemma 4 26B · 4B active | 20.2 t/sFP16 | 78.4 t/sQ5_K_S |
Change the context, RAM or model in the calculator: M1 Ultra 128GB · AMD RX 7900 XTX
Every report on each card, with its source: M1 Ultra 128GB · AMD RX 7900 XTX