El Capitan (LLNL)

El Capitan is a Cray EX255a/MI300A supercomputer at LLNL. It achieved a max HPL score of 1.809 EFLOPS in November 2025 after debuting at 1.742 EFLOPS in November 2024.

System overview

As of November 2025, El Capitan has:

• 11,264 Cray EX255a compute nodes¹
• 45,056 AMD MI300A APUs total
• 88 cabinets
• 704 Rabbit blades (8 per cabinet)²
• 34.8 MW peak, 30 MW running HPL²

El Capitan uses a Slingshot-11 fabric in a dragonfly topology.

Node architecture

Each Cray EX255a node has:

• 4x AMD MI300A APUs (see Specifications)
• 512 GB HBM3 using 8-high stacks
• Fully interconnected sockets

Storage subsystem

El Capitan features two storage subsystems:²

• 8 Rabbit blades per rack, providing near-node-local storage on the Slingshot fabric
• A global Lustre file system named Merced

Footnotes

1. El Capitan debuted with 87 cabinets (11,136 nodes), but the November 2025 HPL run included an 88th cabinet which (I think) was the original test system. I assume this test rack had the same 128 nodes per rack, 4 APUs per node, and 8 rabbits per rack. ↩

2. TOP500 Supercomputers – SC24 Schedule ↩ ↩² ↩³