How one x16 slot drives 8 GPUs: dual PCIE-switch expansion board teardown
TheZachMueller · x · 2026-10-10
- The author breaks down a GPU expansion board with two PCIE switches inside, letting a single host x16 slot drive 8 GPUs (9 in cascade setups).
- Two wiring options: direct connect (two x16-to-4x-x8 MCIO cables) or cascade (one x16 to 2x x8 MCIO), differing in per-GPU bandwidth budget.
- Each switch on the board offers 104 PCIE lanes; a 144-lane variant ($1000 more) buys more P2P bandwidth between GPU groups. Total 208 lanes, with 176–192 usable for GPUs and NVMe drives.
Related event: Teardown: Dual-Switch PCIe Board Drives 8 GPUs From a Single x16 Slot(8 posts)→
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