No idea. Even though the current RAM is off-die, it's still integrated into the architecture (and soldered).So there's hope for a new Mac Pro with upgradable RAM?
There's been speculation that the MacPro might offer two tiers of RAM: The existing soldered RAM (up to a max of 12 GB x 32 = 384 GB for the "Extreme", and 768 GB if they offer a 2x Extreme*), which can be supplemented with slower (because it's placed further away) user-replaceable RAM. But I don't know how that would work with their UMA (Unified Memory Architecture).
Alternately, they might switch from LPDDR5, which currently seems to max out at 12 GB/module (they're using 2 x 12 GB modules in the 24 GB M2 Air), to DDR5, which Samsung is now producing in 24 GB modules. That would give 24 GB x 32 = 768 GB in the Extreme, and 1536 GB in a hypothetical 2x Extreme; the latter would equal the max RAM available from the 2019 Intel Mac Pro.)
*32 GB DDR5 memory chips are in the pipeline which, if they switched to DDR5, would give 1024/2048 GB for an Extreme/2x Extreme, respectively. But based on the article I linked, it doesn't look like those will be available until 2024-2025 (unless another supplier is futher along than Samsung).
*Note also that, if someone is using all the cores, and the Extreme's 384 GB isn't enough, then the 2 x 384 GB on a 2x Extreme may not solve the problem, since it's still the same GB RAM/core.
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