Timing- and power-driven ALU design training using spreadsheet-based arithmetic exploration

We describe master-level design training that combines ALU design exercises based on commercial synthesis tools and arithmetic explorations based on spreadsheets. Despite its limited complexity, the ALU has a few important properties that make it suitable for our training; 1) the ALU subcircuits are diverse and contain both short and long timing paths, 2) timing-driven design is called for, since the ALU is a performance bottleneck, and 3) the ALU is continuously used, making power dissipation an important design parameter. After enforcing strict timing constraints during synthesis of the ALU, the students need to reconsider how to implement the arithmetic block, which initially is too slow. Here, performing arithmetic explorations inside an innovative spreadsheet environment helps to visualize circuit implementation tradeoffs. The final phase in the design training focuses on power analysis and demonstrates that the choice of timing constraint impacts power dissipation.