Is unified memory on Mac Studio M3 Ultra 256GB as fast as VRAM for Llama 3.3 70B Instruct?

Not always. Mac Studio M3 Ultra 256GB can often fit larger models thanks to unified memory, but a discrete GPU with dedicated high-bandwidth VRAM may still decode faster once the model fits. For this combination, the important distinction is capacity versus sustained throughput.

Can Llama 3.3 70B Instruct run on Mac Studio M3 Ultra 256GB?

YES — Runs Great

C45Usable

Estimated from fit model

Llama 3.3 70B Instruct needs ~79.5 GB VRAM. Mac Studio M3 Ultra 256GB has 184.3 GB. With Q4_K_M quantization, expect ~13 tok/s.

Runtime: llama.cppCapacity: RoomyBandwidth: HighStack: StandardBottleneck: Balanced

Operating mode

Choose the run profile you care about

Interactive favors responsiveness, while light API and scale-out lean harder on serving readiness. The fit stays the same, but the recommendation lens changes.

Current mode

Balanced

Balanced for general local use. Keeps the ranking neutral across personal and serving workflows.

Capabilities:

Select quantization to explore

Q4_K_M (Medium quality) — 79.5 GB, 13.0 tok/s, Runs well

79.5 GB required184.3 GB available

43% VRAM used

Fit status

Runs well

Decode

13.0 tok/s

TTFT

14844 ms

Safe context

221K

Memory

79.5 GB / 184.3 GB

Memory breakdown

Weights42.7 GB

KV Cache8.2 GB

Runtime0.9 GB

Headroom27.6 GB

See how fast it feels

See how fast it feelsLlama 3.3 70B Instruct on Mac Studio M3 Ultra 256GB
1st promptCold start — includes initialization
>What is local AI inference?
Local AI inference means running an AI language model directly on your own hardware — your laptop, desktop, or server — instead of sending requests to a remote cloud API.

When you run inference locally the model weights are loaded into your GPU or unified memory. Each token you generate requires reading those weights from memory, so memory bandwidth is the main bottleneck for decode speed.

Key benefits of running locally:
  - Full privacy: your prompts never leave your machine
  - No per-token cost or rate limits
  - Works offline once the model is downloaded
  - Latency depends only on your hardware
2nd promptWarm — model ready, no init overhead
>How much VRAM do I need?
It depends on the model size and quantization level. A rough rule of thumb:

  Model size     Q4 (4-bit)    Q8 (8-bit)    FP16
  7B params      ~4.3 GB       ~7.5 GB       ~14 GB
  13B params     ~7.9 GB       ~13.9 GB      ~26 GB
  70B params     ~42.7 GB      ~74.9 GB      ~140 GB

Most people use 4-bit quantization (Q4_K_M) which gives 90-95% of full quality at a fraction of the memory. A 24 GB GPU can comfortably run most 7B-13B models.
Estimated: 13.0 tok/s decode · 14.8s TTFT (warm) · 33 tok/s prefill

What limits this setup

This setup is broadly balanced for this model.

Shared-memory contention still exists

The OS, browser, and inference runtime all compete for the same physical memory pool, so real-world headroom is less forgiving than raw capacity suggests.

Best improvement path

Performance by workload

Workload	Grade	Fit	Decode	TTFT	Context
Chat	C	Runs well	13.0 tok/s	8097 ms	221K
Coding	C	Runs well	13.0 tok/s	14844 ms	221K
Agentic Coding	C	Runs well	13.0 tok/s	21591 ms	221K
Reasoning	C	Runs well	13.0 tok/s	17542 ms	221K
RAG	C	Runs well	13.0 tok/s	26988 ms	221K

Quantization options

How Llama 3.3 70B Instruct (70B params) fits at each quantization level on Mac Studio M3 Ultra 256GB (184.3 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	27.3 GB	Low	D39
Q3_K_S	3	34.3 GB	Low	D40
NVFP4	4

Get started

Copy-paste commands to run Llama 3.3 70B Instruct on your machine.

Run

lms load hf-maziyarpanahi--llama-3-3-70b-instruct-gguf && lms server start

Upgrade options

Hardware that runs Llama 3.3 70B Instruct well

AMD Instinct MI350X 288GBBudget pick

288 GB VRAM (+32)8000 GB/s (+7181)

Raises estimated decode speed by about 952%.136.8 tok/s decode

Raises estimated decode speed by about 952%.

Adds memory headroom for longer context windows and future model growth.

~$8,000 MSRP

AMD Instinct MI300X 192GBBest value

5300 GB/s (+4481)

Raises estimated decode speed by about 645%.96.8 tok/s decode

Raises estimated decode speed by about 645%.

~$15,000 MSRP

Frequently asked questions

Can Mac Studio M3 Ultra 256GB run Llama 3.3 70B Instruct?

Yes, Mac Studio M3 Ultra 256GB can run Llama 3.3 70B Instruct with a C grade (Runs well). Expected decode speed: 13.0 tok/s.

How much VRAM does Llama 3.3 70B Instruct need?

Llama 3.3 70B Instruct (70B parameters) requires approximately 79.5 GB of memory with Q4_K_M quantization.

What is the best quantization for Llama 3.3 70B Instruct?

The recommended quantization for Llama 3.3 70B Instruct is Q4_K_M, which balances quality and memory efficiency.

What speed will Llama 3.3 70B Instruct run at on Mac Studio M3 Ultra 256GB?

On Mac Studio M3 Ultra 256GB, Llama 3.3 70B Instruct achieves approximately 13.0 tokens per second decode speed with a time-to-first-token of 14844ms using Q4_K_M quantization.

Can Mac Studio M3 Ultra 256GB run Llama 3.3 70B Instruct for coding?

For coding workloads, Llama 3.3 70B Instruct on Mac Studio M3 Ultra 256GB receives a C grade with 13.0 tok/s and 221K context.

What context window can Llama 3.3 70B Instruct use on Mac Studio M3 Ultra 256GB?

On Mac Studio M3 Ultra 256GB, Llama 3.3 70B Instruct can safely use up to 221K tokens of context. The model's official context limit is —, but available memory constrains the safe maximum.

See all results for Mac Studio M3 Ultra 256GB See all hardware for Llama 3.3 70B Instruct

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