Milestones
- Colossus online with 100,000 H100s after ~122 daysSep 2024Complete.
- Expanded to about 200,000 GPUs2025Complete.
- Shelby County air permit for gas turbinesJul 2025Complete.
- Colossus 2 gigawatt-scale buildNowCurrent milestone.
Most important updates
- 5 Jun 2026
- 6 May 2026
- 10 Mar 2026
- 17 Jan 2026
- 2 Sep 2024
Upcoming
- Oct 2026Google's full-rate rental of about 110,000 GPUs on xAI clusters starts ($920M a month) (next)
Current obstacles
- Power and permitsMemphis power has come from on-site turbines and new substations, drawing regulator attention.
Physics limits
- Almost all power becomes heatNearly every watt a chip draws ends up as heat. A 72-GPU rack draws about 120 to 130 kW, over 10x an old server rack, so air can't cool it; liquid loops must.
- A gigawatt is a power plant1 GW running all year is about 8.8 TWh, the output of a large nuclear reactor. Sites need dedicated generation or new high-voltage lines, which take years to build.
- At this scale something always breaksMeta logged 419 unexpected interruptions in 54 days on a 16,384-GPU Llama 3 run, about one every 3 hours. Bigger clusters fail more often and must checkpoint constantly.
How it works
Reuse an old factory
Colossus 1 went into a former Electrolux plant in Memphis, from empty building to 100,000 H100 GPUs in about 122 days.
Turbines and batteries
Mobile gas turbines supplied power before the full grid hookup; Tesla Megapacks smooth the sudden load swings when training jobs start and stop.
Ethernet at huge scale
GPUs talk over NVIDIA Spectrum-X Ethernet rather than InfiniBand, which let xAI scale one cluster past 100,000 GPUs.
The next gigawatt
Colossus 2 in Memphis runs GB200 and GB300 racks, fed by a gas plant built across the state line in Southaven, Mississippi.
Update log
Fri 5 Jun
- Major: PressCommercial
Wed 6 May
- Major: BlogCommercial
Tue 10 Mar
- Minor: PressRegulatory
Sat 17 Jan
- Major: XHardware
Wed 2 Jul 2025
- Minor: PressRegulatory
Mon 2 Sep 2024
- Major: XHardware
About xAI
xAI
Grok models, Colossus supercomputer
xAI, founded by Elon Musk in 2023, makes the Grok models used on X, which it absorbed in 2025. It built its Colossus supercomputer in Memphis unusually fast. SpaceX bought xAI in February 2026, valuing it at $250B.
- Bought by SpaceX on 2 February 2026, in a deal valuing SpaceX at $1T and xAI at $250B.
- Colossus went from empty building to 100,000 H100 GPUs in about four months in 2024.
- Grok 4 (July 2025) and Grok 4.1 (November 2025) ranked near the top on reasoning tests.
- Founded
- 20233 yrs
- Headquarters
- United States
- Status
- Subsidiaryof SpaceX
- Valuation
- $250BSpaceX-ownedFeb 2026
- Raised
- $32B3 rounds
- Last round
- Series E · $20BJan 2026
- Works in
- AIFrontier modelsComputingSpaceflight
- Coverage
- 2 programs · 18 updateslatest 19d agochecked 25 Sep
- Partners
- XTesla
- Suppliers
- NVIDIA
- Acquired by
- SpaceX
- People
- Elon MuskFounder