> "This uses 4266 MT/s LPDDR4X SDRAM (synchronous DRAM) and is mounted with the SoC using a system-in-package (SiP) design."
> Which implies to me that some kinds of LPDDR is indeed HBM and that what's on the M1 isn't something which can be replaced by drop in RAM.
Sibling comment already outlined that HBM is unique & different from LPDDR. Using LPDDR means it's definitely not HBM.
But you can definitely hit LPDDR4 at 4266 MT/s speeds with drop-in RAM. That's DDR5, which in the "initial" spec goes all the way to 6400 MT/s. More relevantly, DDR5-4800 (so 4800 MT/s) modules are among the first to actually be manufactured: https://www.anandtech.com/show/16142/ddr5-is-coming-first-64...
> Which implies to me that some kinds of LPDDR is indeed HBM and that what's on the M1 isn't something which can be replaced by drop in RAM.
Sibling comment already outlined that HBM is unique & different from LPDDR. Using LPDDR means it's definitely not HBM.
But you can definitely hit LPDDR4 at 4266 MT/s speeds with drop-in RAM. That's DDR5, which in the "initial" spec goes all the way to 6400 MT/s. More relevantly, DDR5-4800 (so 4800 MT/s) modules are among the first to actually be manufactured: https://www.anandtech.com/show/16142/ddr5-is-coming-first-64...