Soldered Memory

In every unified-memory box here, the RAM is soldered to the board (LPDDR5X) and cannot be upgraded after purchase. That's a physical consequence of the wide, fast memory buses these chips need — a Strix Halo box's 256-bit LPDDR5X-8000 or an M3 Ultra's 819 GB/s setup only works because the memory sits right next to the processor. So you must buy the 128GB (or whatever) config up front; there's no adding more later. It's the single most important 'buy it right the first time' constraint on these machines.

Size memory for the biggest model you'll want over the life of the box, not today's — you can't add a stick later. When capacity is fixed, over-buying by one tier is cheaper than being stuck under-provisioned.