Crossing the Laguna

What this FPGA cross-die timing interview question tests

This is an easy question on physical design constraints in large-scale FPGA implementations. It probes whether a candidate understands the architectural limitations of multi-die parts—specifically Xilinx UltraScale+ (VU5P, VU9P, VU13P) and Versal devices—and how die-to-die communication affects timing closure and latency.

Interviewers ask this to identify engineers who think beyond RTL and synthesis. The question rewards knowledge of how Laguna tiles physically constrain signal crossing between SLRs (Super Logic Regions), and what design practices—timing budgeting, placement discipline, and clock strategy—are needed to meet aggressive frequency targets. Low-latency trading and HFT firms care deeply about these constraints because unmanaged cross-die delays can waste hard-won nanoseconds.

• SLR (Super Logic Region) architecture and interposer connectivity
• Laguna tile bandwidth and latency characteristics
• Timing closure strategy for multi-die designs
• Placement and routing discipline across die boundaries