Musk halved the memory in Tesla's Optimus chip; Micron says a humanoid needs more than 200GB

On October 1 Elon Musk said Tesla had cut the memory on its AI5 chip in half↗ and on the successor AI6 by a third, calling the cut "the only way to get enough volume for Optimus production" ¹. AI5 is the processor behind Tesla's▼−1.09% — Tesla, down 1.09 percent today autonomous-driving and robotics work, and Optimus is its humanoid robot ². Musk said the cut "greatly" reduces cost, and that "we think this will have a negligible effect" on the robot's performance ¹.

So the constraint on building Optimus at volume is no longer compute or intelligence but memory: the low-power DRAM, the workhorse chips in phones and laptops. The post Musk was answering had done the arithmetic: a world of 10 billion robots at 200GB each needs 2 trillion GB, against roughly 45 billion GB of DRAM the world produces in a year ¹. A day later he nudged AI5 up to 96GB↗, so Tesla would not be the only buyer on the minimum LPDDR5 configuration ².

The memory seller specs a humanoid at twice the thinned AI5 chip

Micron▼−5.17% — Micron, down 5.17 percent today, the US memory maker, told investors↗ the same week that a humanoid will need more than 200GB of memory and terabytes of storage per unit, comparable to an autonomous vehicle, and that physical AI becomes a real memory market by the end of the decade ³. Chief executive Sanjay Mehrotra is specifying a robot at roughly twice the memory of the AI5 chip Tesla just thinned. One side of that trade is wrong about where robot capability comes from.

Musk's defense of the cut is mechanical: memory bandwidth, not capacity, is what limits the robot ³. Today's Optimus volume is reportedly a first large-scale component order for about 5,000 units, against a stated goal of one million a year ³. The spec dispute sits squarely between those two numbers.

The bridge to that volume is borrowed

The money arrived on September 29, when Tesla opened $30 billion in credit lines with Citigroup and Wells Fargo↗, money it says could help scale the Cybercab robotaxi, the Semi and Optimus ⁴⁵. The lines replace a $5 billion facility and sit undrawn, which the company expects to keep that way this year ⁴. Capital spending is guided to $25 billion in 2026, up from $8.5 billion in 2025 ⁴.

In the June quarter, capital spending passed operating cash flow, and Tesla booked its first cash-flow-negative quarter since early 2024 ⁴⁹.

The roadmap now runs through the memory market twice

Musk moved that market himself this week. After China's ChangXin Memory Technologies reported design advances in memory chips, he wrote that the low-power memory standard used in phones and laptops is one China "seems to be solving fast," while stacked high-bandwidth memory will be harder to crack ⁶. The selloff erased $108 billion↗ from the market value of Micron, SK Hynix and SanDisk, three of the world's biggest memory makers, that day ⁶. Micron fell another 4.56% on Tuesday↗ ⁷.

Rationing memory to ship product is real engineering, and Musk deserves credit for making the trade instead of missing the ramp. The trade left a dependency in place of the shortage: Optimus now rests on memory suppliers' pricing this year and, by Musk's own account, on how fast China masters the standard chips ⁶. Tesla reports third-quarter results on October 21↗ ⁸. What decides this story will not be in the income statement; it is whether "negligible" survives contact with buyers and with the road.