Comment by MobiusHorizons

I know everyone on this site loves to hate on soldered ram, but my impression is most people don’t understand that soldered ram is not the same thing as regular ram modules. They are literally different memory chips (LPDDR vs DDR) . When built to a specific chip my understanding is you can design for tighter timings and higher bandwidth which is important for the gpu. The M1 shipped with very fast LPDDR4X running at 4266MT/s which was even pretty fast by XMP desktop speeds at the time (2020). There are real engineering advantages to soldered ram especially if the memory controller has need designed with to take advantage of it. I guess it is similar to how gpu memory configurations are specialized and not modular.