NVIDIA ($NVDA) would incur an additional 60kW of power and $2M of cost per rack by replacing short copper cables with optical links, according to Bernstein's expert assessment with former NVIDIA leader Brad Smith. In the Vera Rubin architecture, NVLink switching sits centrally in the rack to connect compute trays above and below through roughly 5,000 short copper cables. These passive copper links operate across distances up to 18 inches at 200Gbps signaling speeds, retaining printed circuit boards with copper traces. Prior to accelerated computing workloads running across up to 1 million GPUs, copper handled roughly 90% of data center interconnects alongside 8% multi-mode optics and 2% single-mode optics, because electrical wiring provides unmatched capital and thermal efficiency. Physics dictates that achievable copper reach compresses as signaling speeds rise, falling from roughly 100m at 1Gbps to 2.5m at 100Gbps, 18 inches at 200Gbps, and 12 inches at 400Gbps. At 400Gbps, passive copper reach becomes impractical as electron radiation degrades signal integrity along the conductor. To bypass cabling congestion without abandoning electrical transmission, Feynman-era architectures approaching 1MW per rack integrate four blade assemblies directly into a midplane board with back-mounted NVLink switches. While active electrical cables with retimers can extend 200Gbps reach to 2 meters, they introduce roughly $1,200 of unit cost and 100 to 200 nanoseconds of latency. Server makers will therefore keep copper inside the rack until package-level input-output demands exceed short-reach electrical limits. #AdvancedPackaging# #NVIDIA# #TEConnectivity# #OpticalNetworking# #Networking# Report date: 2026-10-15 · Bernstein