This article argues that local-AI performance on Macs depends on memory bandwidth, not CPU cores, GPU cores, or the Neural Engine. Using a simple formula (bandwidth ÷ model size × efficiency), it shows a 2021 M1 Max outperforms a 2024 M4 base chip by over 3× on a 7B model. It recommends buying used Max-tier machines and highlights lineup quirks like the M3 Pro’s bandwidth regression.

• Memory bandwidth, not CPU/GPU/Neural Engine specs, determines local-AI token generation speed on Macs
• A 2021 M1 Max (400 GB/s) hits ~64 tok/s on a 7B model vs. ~19 tok/s on a base 2024 M4 (120 GB/s) — over 3× faster despite being three years older
• Tier jumps (base→Pro→Max) matter far more than generational upgrades: four generations of base chips only went from 68 to 120 GB/s, while switching tiers can triple or quadruple bandwidth
• Used Max-tier MacBook Pros often cost the same as a new M4 MacBook Air but outperform it on every local-AI task except power efficiency and media engines, making RAM/bandwidth the specs to prioritize when buying used