3 Things to Know About the iMac M3’s Storage Design

The storage controller is built into the M3 chip itself Apple integrates a proprietary NVMe controller directly into the M3 SoC, not on a separate module.

The NAND flash is soldered to the logic board The memory chips are attached to the board, but the controller is on the chip, making the whole storage system sealed and non-standard.

You cannot upgrade or replace the storage There are no M.2 or SATA slots, and no user-serviceable parts. What you buy is what you get for the life of the computer.