The short version
- Memory decides which models fit. Buy as much as you can; it can't be upgraded later.
- Memory bandwidth decides how many tokens a second you get. Max and Ultra chips have three to twelve times the bandwidth of the base chip of their generation.
- Best value for most people: a Mac mini or MacBook Pro with a Pro chip and 64 GB. For the biggest models: Mac Studio with Max or Ultra.
- Check real numbers on MLX Bench before you buy.
1Why memory and bandwidth decide everything
A language model writes one token at a time, and for each one it reads every active weight from memory. So the speed limit for a single conversation is roughly memory bandwidth divided by the size of the active weights. In llama.cpp's public benchmarks, real generation reaches 43% to 80% of that limit on Apple chips (llama.cpp).
Reading your prompt is different: that part is limited by compute, which is why M5-generation chips, with neural accelerators in the GPU, process prompts several times faster than earlier ones (Apple).
2Every chip, compared
| Chip | Max memory | Bandwidth | Found in |
|---|---|---|---|
| M5 | 32 GB | 153 GB/s | MacBook Air, 14-inch MacBook Pro |
| M6 | 32 GB | 170 GB/s | Mac mini |
| M4 Pro | 64 GB | 273 GB/s | Mac mini, MacBook Pro |
| M5 Pro | 64 GB | 307 GB/s | MacBook Pro, Mac mini |
| M4 Max | 128 GB | 546 GB/s | MacBook Pro, Mac Studio |
| M5 Max | 128 GB | 614 GB/s | MacBook Pro, Mac Studio |
| M3 Ultra | 512 GB | 819 GB/s | Mac Studio (2025) |
| M5 Ultra | 512 GB | 1.2 TB/s | Mac Studio (2026) |
Older chips still work well when they have the memory. An M1 Max or M2 Max with 64 GB reads at 400 GB/s, more than any base chip today, and often costs far less second-hand.
3Which Mac to buy
Just trying it: MacBook Air or Mac mini with 16 to 32 GB
Runs 7B to 14B models comfortably and 30B-class models at 32 GB. Fine for chat, writing and light coding help.
Best value: Pro chip with 64 GB
A Mac mini or MacBook Pro with M4 Pro or M5 Pro holds 70B-class models and runs mid-size models at a good pace. The sweet spot for most developers.
Serious local AI: Max chip with 128 GB
Runs gpt-oss-120b (about 65 GB at 4-bit) on a laptop; from Apple's bandwidth figure, the theoretical ceiling for one stream on M5 Max is about 225 tokens a second. The best portable choice.
The biggest models: Mac Studio with Ultra
Up to 512 GB at 1.2 TB/s with M5 Ultra holds models with hundreds of billions of parameters on one desk. For even bigger models, Macs can be joined into a cluster over Thunderbolt 5: see Mac AI clusters.
4Make the Mac pay its way
A Mac bought for AI spends most of its time waiting. MLX Node is a free app that lends that spare capacity to MLX Network, running AI jobs on the same MLX framework and earning MLX Tokens for verified work. A dedicated seat matched to the chip multiplies what it earns: a Pro seat runs at full rate on a Pro or Max chip, an Ultra seat on an Ultra chip.
Compare your Mac on MLX Bench first: it shows measured tokens per second for open models on every chip.
5Questions
- Is 16 GB enough for a local LLM?
- Yes for models up to about 14B parameters at 4-bit. For larger models, or long contexts, 32 GB or more is much more comfortable.
- Mac Studio or MacBook Pro for LLMs?
- Both come with Max chips and up to 128 GB. The MacBook Pro is portable; the Mac Studio stays cooler under long loads and is the only Mac with Ultra chips and up to 512 GB.
- Is a Mac better than an Nvidia GPU for local AI?
- For the largest models at home, often yes: a Mac's unified memory can hold far more than a consumer graphics card's memory. A high-end Nvidia card is faster on models that fit in its memory.
- Does the M5 make LLMs faster?
- Yes, mainly for reading prompts: Apple measured the first token arriving 3.3 to 4.1 times sooner on M5 than M4 with MLX. Generation speed grows with memory bandwidth, which rose 28% from M4 to M5.
Sources
- llama.cppgithub.com
- Applemachinelearning.apple.com
- M4 Pro and Maxapple.com
- M5apple.com
- M5 Pro and Maxapple.com
- M6 and M5 Ultraapple.com
- M3 Ultrasupport.apple.com