224G PAM4 Interconnect

Overview

224G PAM4 Interconnect refers to the current generation of high-speed copper data links running at 224 Gbps per lane using PAM4 (4-level pulse amplitude modulation), succeeding 112G PAM4 as the dominant speed class for scale-up AI rack interconnects. The 224G transition is driven by the need to increase bandwidth density within AI racks connecting GPU clusters without proportionally increasing the number of cables and connectors.

The key system constraint for 224G copper links is the bump-to-bump channel budget: GPU-to-switch chip passive copper paths must typically stay within approximately 30 dB or less total insertion loss at 53 GHz, with aggressive implementations targeting around 24 dB. Full Luxshare-Tech stack (KOOLIO 224G CPC + Optamax 31 AWG + Intrepid NEXUS) achieves 24.13 dB at 53 GHz. The 224G ecosystem is governed by IEEE 802.3dj (at Draft 2.0 as of October 2025) and by multi-source connector specifications from backplane manufacturers. Future evolution toward 448 Gbps copper is expected to continue.