3 Things to Know About the M4 Max MacBook Pro 16-Inch’s 128GB Memory Limit
Regarding the MacBook Pro: 1. Unified memory is soldered into the M4 Max chip, so you cannot upgrade it later. Choose your configuration carefully at order time.
The maximum memory Apple offers is 128GB, but only on the highest-end M4 Max model. Lower-tier M4 Max chips cap at lower amounts.
If you need 128GB, you must select it when buying the laptop. There is no way to add more memory after purchase.