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C h a p t e r 2 | I n t e r c o n n e c t D e s i g n a n d S i g n a l I n t e g r i t y i n P r a c t i c e Standardized form factors can also heavily influence how engineers route PCIe signals through compact embedded platforms. For instance, M.2 provides four PCIe lanes in a dense footprint but requires strict control of trace breakout and grounding. As a result, many are turning to PICMG ® COM-HPC ® , an open standard that defines high-density connectors that support PCIe 5.0 and 6.0. The connector's finer 0.635mm pitch and optimized pin mapping allow longer trace paths without violating loss budgets, though carrier boards still need deliberate layer planning to keep loss and crosstalk consistent in all lanes. In the same vein, many embedded systems are realizing the benefits of cable-based PCIe, as cables isolate the signal path from PCB variability. Here, copper Twinax cables can reduce insertion loss over longer distances and The most important idea beyond PCIe 4.0, is keeping in mind that signal integrity (SI) is a non negotiable for the digital design. That means, even before validation comes into the picture, teams need to rely on simulations with the most recent and accurate software." bypass complex board routing. They also decouple mechanical constraints so that engineers can reposition modules without re-spinning PCBs. For even greater reach, optical PCIe links extend channels to support distributed architectures across racks or remote enclosures. Such extended channels need precise equalization settings. Validation and Simulation As SI constraints tighten, validation and simulation tools have become necessary. Designers should prioritize pre-layout simulation to estimate insertion loss, crosstalk, and reflections before committing to a board design. By employing accurate models of connectors, cables, and materials at this stage, engineering teams can determine whether a system meets compliance requirements and adjust stackups or component choices accordingly. Javier Loranca Coutiño Power Electronics Engineer, Bosch 16 8 Experts Discuss PCIe for Emerging Embedded Systems