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Mac Studio M3 Ultra 256GB vs NVIDIA GeForce RTX 4090

For running models locally, priced in the UK. At 128k context the first runs 42 models fully in memory, the second 9.

In short

The Mac Studio M3 Ultra 256GB has more memory for models: 256 GB against 24 GB. At 128k context the Mac Studio M3 Ultra 256GB runs 42 of the models we track fully in memory and the NVIDIA GeForce RTX 4090 9; only the Mac Studio M3 Ultra 256GB holds DeepSeek V4 Flash. On the models both run fully in memory, the NVIDIA GeForce RTX 4090 is about 1.2× as fast as the Mac Studio M3 Ultra 256GB (estimated, median across models). In the UK the Mac Studio M3 Ultra 256GB costs £8,499 at eBay (used) and the NVIDIA GeForce RTX 4090 £6,015 at Amazon: the NVIDIA GeForce RTX 4090 is £2,484 cheaper.

Updated . Speeds are estimates; how they are worked out.

Mac Studio M3 Ultra 256GB

£7,499

eBay

Add to build
NVIDIA GeForce RTX 4090

£6,015

Amazon

Add to build

Specifications

SpecMac Studio M3 Ultra 256GBNVIDIA GeForce RTX 4090
ChipApple M3 Ultra (80-core GPU)–
Memory bus1024-bit384-bit
Memory bandwidth819 GB/s1,008 GB/s
FP16 compute28 TFLOPS165 TFLOPS
SoftwareMetalCUDA
Unified memory256 GB–
GPU can use by default192 GB–
GPU can use, tuned248 GB–
Operating systemmacos–
ProcessorM3 Ultra 32-core–
Storage2000 GB–
GPU–GeForce RTX 4090
Memory–24 GB GDDR6X
Board power–450 W
PCIe generation–Gen 4
PCIe lanes–x16

What each runs

Estimated decode speed with the most precise quant that fits each one est.

ModelMac Studio M3 Ultra 256GBNVIDIA GeForce RTX 4090
DeepSeek V4 Flash14tok/sUD-Q4_K_XLwon't run
GLM 5.3 Flash18tok/sUD-Q4_K_XLwon't run
Qwen 3.8 Flash Next5tok/sQ8_0won't run
Qwen 3.8 27B14tok/sQ8_0offload
MiniMax M2.78tok/sUD-Q5_K_Mwon't run
Qwen 3.5 122B-A10B23tok/sQ8_0offload
Qwen 3.6 27B14tok/sQ8_0offload
Qwen3 Coder Next43tok/sQ8_0won't run
gpt-oss 120B40tok/sMXFP4won't run
Nemotron 3 Super 120B-A12B23tok/sQ8_0won't run
Gemma 4 31B12tok/sQ8_0offload
Mistral Small 4 119B30tok/sQ8_0offload
Qwen 3.6 35B-A3B55tok/sQ8_0offload
Qwen 3.5 27B14tok/sQ8_0offload
Gemma 4 26B-A4B45tok/sQ8_068tok/sUD-Q4_K_M
GLM 4.5 Air8tok/sQ8_0won't run
Qwen 3.5 35B-A3B55tok/sQ8_0offload
Qwen3 Next 80B-A3B50tok/sQ8_0won't run
GLM 4.7 Flash26tok/sQ8_0offload
Devstral Small 2 24B11tok/sQ8_0offload
Nemotron 3.5 Lightning 30B-A3B76tok/sUD-Q6_K_XLoffload
Kimi Linear 48B-A3B75tok/sQ8_0offload
gpt-oss 20B57tok/sMXFP466tok/sMXFP4
Qwen3 Coder 30B-A3B20tok/sQ8_0offload
Qwen3 32B8tok/sQ8_0won't run
Gemma 4 12B35tok/sQ8_041tok/sQ8_0
Qwen 3.5 9B38tok/sQ8_045tok/sQ8_0
Gemma 3 27B13tok/sQ8_0offload
Mistral Small 3.2 24B11tok/sQ8_0offload
DeepSeek R1 Distill Qwen 32B8tok/sQ8_0won't run
Llama 3.3 70B5tok/sQ8_0won't run
Ministral 3 14B15tok/sQ8_0offload
Qwen3 14B14tok/sQ8_0offload
DeepSeek R1 0528 Qwen3 8B19tok/sQ8_0offload
Qwen3 8B19tok/sQ8_0offload
Phi-4 14B13tok/sQ8_0offload
Qwen 3.5 4B60tok/sQ8_071tok/sQ8_0
Ministral 3 8B20tok/sQ8_027tok/sQ4_K_M
Granite 4.2 8B17tok/sQ8_0offload
Gemma 4 E4B44tok/sQ8_052tok/sQ8_0
LFM2.5 8B-A1B43tok/sQ8_050tok/sQ8_0
Llama 3.1 8B22tok/sQ6_K27tok/sQ5_K_M

Questions

Which is better for local AI, the Mac Studio M3 Ultra 256GB or the NVIDIA GeForce RTX 4090?
Choose the Mac Studio M3 Ultra 256GB to run bigger models. Choose the NVIDIA GeForce RTX 4090 for speed. Choose the NVIDIA GeForce RTX 4090 to spend less.
Which can run bigger models, the Mac Studio M3 Ultra 256GB or the NVIDIA GeForce RTX 4090?
At 128k context the Mac Studio M3 Ultra 256GB runs 42 of the models we track fully in memory and the NVIDIA GeForce RTX 4090 9; only the Mac Studio M3 Ultra 256GB holds DeepSeek V4 Flash.
Which is faster for local AI, the Mac Studio M3 Ultra 256GB or the NVIDIA GeForce RTX 4090?
On the models both run fully in memory, the NVIDIA GeForce RTX 4090 is about 1.2× as fast as the Mac Studio M3 Ultra 256GB (estimated, median across models).
What is the price difference between the Mac Studio M3 Ultra 256GB and the NVIDIA GeForce RTX 4090?
In the UK the Mac Studio M3 Ultra 256GB costs £8,499 at eBay (used) and the NVIDIA GeForce RTX 4090 £6,015 at Amazon: the NVIDIA GeForce RTX 4090 is £2,484 cheaper.

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