The M5 Ultra Mac Studio Was Tested at 768GB of RAM. Will It Actually Ship That Way?

Quick Verdict: Apple has reportedly tested the M5 Ultra at up to 768GB of unified memory — more than the 512GB ceiling the M3 Ultra launched with, back when Apple could still offer it. Whether that capacity actually reaches a shipping configuration in October is a separate question, and recent history says don't count on it.

This is the direct follow-up to our local AI workstation cost breakdown, where the honest advice was "wait until October if you can." Here's what's actually worth waiting for.

The Precedent That Matters Here

The M3 Ultra Mac Studio launched with a genuinely remarkable spec: up to 512GB of unified memory, enough for Apple to publicly claim it could run models over 600 billion parameters entirely in memory — the most RAM ever offered in a personal computer. That was the story in early 2025.

By March of this year, the 512GB option was gone. Apple quietly capped the line at 256GB and raised the price of the remaining upgrade by $400. And as of this writing, even the 256GB tier is unavailable — the only M3 Ultra Mac Studio you can currently order tops out at 96GB, and it's backordered into October. The stated reason both times: global supply constraints from AI's demand on the memory market, the same shortage we've covered in detail in our RAM pricing piece.

That's the pattern to keep in mind for everything below: Apple has repeatedly shown it's willing to engineer for a higher ceiling than it can actually supply.

What's Rumored for M5 Ultra

Pulling from the most specific reporting available:

  • Memory bandwidth: Rumored at 1,000–1,100GB/s, a substantial jump attributed to the M5 Max's revised architecture, which is built to scale more efficiently when two dies are fused via UltraFusion into an Ultra chip.
  • Cores: Reports vary — some point to roughly 36 CPU cores and 84 GPU cores, others suggest the core count stays close to the current M3 Ultra's approximate 32-core CPU / 80-core GPU layout with the real gains coming from architecture and bandwidth rather than raw core scaling.
  • Base memory: The M5 Ultra is reportedly starting at 96GB — unchanged from where the M3 Ultra started (and, notably, exactly where the only currently orderable M3 Ultra configuration sits today). The M5 Max variant is reportedly starting at 36GB.
  • Maximum tested memory: Up to 768GB — a genuinely surprising number given Apple couldn't sustain supply for 512GB on the outgoing chip.
  • NPU: A reported 45% jump in Neural Processing Unit performance over the M4 Ultra, plus something new — a hardware block some reporting refers to as an "Agentic Accelerator," apparently purpose-built for KV-cache management and recursive reasoning loops in AI agent frameworks. If accurate, that's Apple explicitly building silicon for the exact agentic-workflow use case we covered in our workstation cost piece, not just generic AI acceleration.

Reading Between the Numbers

Here's the tension: Apple's own internal testing reportedly went as high as 768GB — 50% beyond the M3 Ultra's original 512GB ceiling. That tells you the engineering headroom exists. It does not tell you what ships.

Given that Apple has now twice pulled back RAM availability on the current generation — first from 512GB to 256GB in March, then from 256GB availability entirely by summer — the realistic expectation for October should be modest. If we had to bet: a shipping ceiling somewhere in the 256GB–384GB range feels far more plausible than the full 768GB Apple reportedly tested, unless memory supply meaningfully loosens between now and launch, which nothing in current forecasting supports happening that fast.

The base 96GB configuration is the safer prediction — it's stayed constant through two generations and through the worst of the shortage, likely because Apple treats it as the price-anchoring entry tier rather than something supply-constrained the same way the high-capacity options are.

What This Means If You're Deciding Whether to Wait

If your use case genuinely needs 256GB+ of unified memory for local model work, October is worth waiting for — but go in expecting the top configuration to be either unavailable at launch or priced at a significant premium over what the 256GB M3 Ultra tier used to cost, the same way Apple raised the 256GB upgrade by $400 the last time supply tightened.

If 96GB is enough for what you're actually doing — which, per our workstation cost breakdown, is genuinely competitive with a $8,000+ DIY dual-GPU Linux box — the M5 Ultra's base configuration plus its bandwidth and NPU improvements over the M3 Ultra may be the more sensible buy the moment it's actually available, rather than holding out for a 768GB configuration that may never reach a "buy now" button.

We'll update this piece the moment Apple confirms real specs and pricing.

Sources: MacRumors — M5 Ultra Mac Studio could launch with up to 768GB RAM, wccftech — M5 Ultra rumored specifications, Macworld — M3 Ultra RAM delay news, 9to5Mac — what's coming with the next Mac Studio refresh, BigGo Finance — Mac Studio 768GB memory reporting