Bypassing Motherboard Copper Traces With Cabled PCIe Gen 6 Over-the-Board Interconnects
At 64 GT/s, traditional motherboard copper traces cause unacceptable signal loss. Server architects are moving high-speed data completely over the board.
The transition to PCIe Gen 6 and next-generation proprietary accelerator fabrics has pushed standard printed circuit board (PCB) design to its physical limits. Operating at a blistering 64 GT/s using PAM4 signaling, high-frequency data signals are incredibly sensitive to attenuation (signal loss) and electromagnetic interference when traveling through standard fiberglass and copper motherboard layers.
To maintain acceptable signal integrity over required system distances, server architects are largely abandoning long PCB traces in favor of over-the-board cabled architectures. Utilizing specialized near-chip connector systems and high-density interface components, high-speed lanes are pulled off the motherboard layers entirely.
These systems utilize ultra-low-loss twinaxial cable jumpers that plug directly into miniature, shielded receptacles positioned immediately adjacent to the CPU or GPU socket. By routing data through high-grade copper cables suspended above the motherboard, hardware designers drastically minimize insertion loss, lower signal latency, and reduce overall board manufacturing costs by minimizing the layer count of the massive baseboard PCB beneath.