Short-reach AI interconnects: AEC beats optics under 10m on cost and power
firstadopter · x · 2026-10-16
Investor-blogger firstadopter shares slides from an OCP Global Summit 2026 talk and concludes that optics is overkill for links under 10 meters — AEC is cheaper and uses less power. Key points from the slides:
- AI clusters scale GPU I/O exponentially (8 → 64 GPUs per generation), with scale-up/scale-out fabrics dominating rack-level connectivity
- Thousands of 1-2 m short-reach links per cluster (switch to NIC) are the workhorse of AI datacenter connectivity
- Interconnect comparison: optics reaches up to 10 km but costs the most (12-15 W per end); passive DAC is lowest power (1-2 W) but only reaches 2-3 m and fails the 112G PAM4 budget; AEC stays under 12 W, reaches 2-7 m, meets PAM4 with margin, and is simple to manage
- 800G AEC for X-rack connectivity: one rack pair uses four cable types chosen by reach (DAC, AEC, optics, RJ45)
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