Apple's 512GB unified memory vs GB300's 252GB 'memory cliff' for dense models
AccBalanced · x · 2026-08-27
CTOAdvisor argues Apple could charge $20K+ for a 512GB M5 Ultra Mac Studio and it would still be a steal for a large class of AI workloads. The comparison: Dell's GB300 deskside, quoted at $148K (list $175K).
The point isn't peak performance. Below 252GB the GB300 is a monster with 7.1TB/s HBM bandwidth, but once a dense model exceeds 252GB, weights spill into far slower system memory — the "memory cliff." The 512GB M5 Ultra has no cliff: the whole model stays in one 1.2TB/s unified memory domain, opening an interesting 252GB–512GB window. Full testing results are forthcoming.
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