In modern semiconductor development, pre-tapeout verification has emerged as one of the most demanding phases of the chip design lifecycle. With multi-million flop architectures, advanced scan structures, and increasingly compressed product schedules, engineering teams must validate design integrity long before fabrication begins. Consequently, verification methods that can improve speed, accuracy, and observability are becoming essential. In particular, gate-level simulation remains a cornerstone of signoff readiness, yet it is often constrained by long runtimes and heavy dependencies across multiple engineering functions.
Sashaank Kasturirangan has contributed to advancing verification efficiency through a practical engineering approach focused on Design for Test (DFT) and gate-level validation. Earlier in his work, he was involved in Scandump verification, a technique used to read and write internal flip-flop states through scan chains in order to diagnose functional hangs and analyze internal system behavior. This area of expertise positioned him to address one of the recurring bottlenecks in complex silicon programs: lengthy simulation cycles during pre-tapeout readiness checks.
Traditionally, verifying scandump functionality required engineering teams to first run complete cold and warm boot sequences so that a design could reach a realistic functional state. Only then could clocks be halted and the contents of internal flops shifted out for analysis. However, for large-scale designs, that process often required between 48 and 52 hours per verification cycle. As a result, bug discovery slowed, debug iterations stretched out, and overall tapeout schedules faced heightened risk.
While earlier industry improvements had moved scan insertion further left into the RTL stage thereby catching issues such as scan stitching failures, pipe imbalances, and clock connectivity earlier in development full gate-level validation still remained necessary. It was at this stage that Sashaank explored an alternative methodology centered on backdoor randomization, which bypasses conventional functional paths and enables direct runtime access to internal states without consuming extensive clock cycles.
Rather than relying on traditional Verilog-based methods that required recompilation whenever randomization states were adjusted, he implemented a multi-layered runtime solution using Perl for design parsing, C/VPI shared libraries for simulator access, and gate-level simulation for execution. This framework enabled engineers to dynamically force randomized values into functional flops while clocks were stopped, thereby reproducing realistic hung-chip states for debug purposes.
The operational impact was significant. Verification runtimes were reduced from 48–52 hours to approximately 16–18 hours, representing an estimated 70–80 percent improvement in debug cycle times. In addition, the approach eliminated recompilation delays that could otherwise consume 24 to 30 hours per iteration. Functional boot dependencies were also reduced, saving another 3 to 4 hours of simulation time in many cases. Therefore, teams were able to begin verification work sooner and iterate more rapidly when issues were found.
Equally important, the methodology appears to have influenced broader program schedules. Pre-tapeout verification timelines that had previously extended to around nine months were shortened by roughly two months through faster validation cycles and reduced inter-team waiting periods. In an industry where schedule movement can affect manufacturing readiness, engineering allocation, and downstream launch plans, such gains can carry substantial strategic value.
At the same time, Sashaank notes that runtime randomization methods require disciplined testbench maintenance. Certain seeds may generate states that are not always functionally realistic, which means refinement and coordination between architects and verification teams remain necessary. Nevertheless, once established, the infrastructure can be reused across multiple projects and teams, creating long-term efficiency benefits.
As silicon systems continue to scale in complexity, verification innovation is increasingly becoming as important as design innovation itself. Work in areas such as dynamic state initialization, faster gate-level debug, and smarter observability tools reflects a wider shift in the semiconductor sector. In that context, methodologies that reduce cycle times without compromising verification quality are likely to play a defining role in future pre-tapeout excellence.
