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Applied Micro Circuits Corporation (AMCC)

Applied Micro Circuits Corporation (AMCC) adopts Questa CDC for their complex clock domain crossing verification.

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CDC by nature is inherently a very difficult process and the tools can be difficult to use. We came back to Mentor for the reason of usability. Compared to other vendors, we were very pleased with the solution and already look forward to using it for future projects.”

Karl Pfalzer, Chief Verification Engineer, AMCC

Complex clock domains require CDC verification 

A recent high-performance network processor presented a new challenge for the AMCC team.  The processor consisted of a PowerPC embedded processor core and a multi-clock domain SoC that includes Ethernet and other standard interfaces. Both parts required CDC verification, but the SoC was more challenging because of the complexity of its clock domains and the signals that pass between them.  It was clear that this design required a more sophisticated and comprehensive CDC verification solution than they had used before.

Mentor’s Questa CDC tool outshines other vendors

When Karl Pfalzer took up his duties as chief verification engineer of this AMCC team, the Mentor Questa CDC tool was already part of their tool suite. However, in performing proper diligence, he evaluated competitive CDC verification tools before committing to Questa CDC. “We came back to Mentor for the reason of usability,” says Mr. Pfalzer.

This was the first project where AMCC was to perform CDC verification at the block level and then at the full chip level, so there was a lot for them to learn. The team received comprehensive training from a Mentor CDC expert on the nature of CDC, its problems, and why a specialized tool is needed to address them. Mr. Pfalzer then worked with the Mentor specialist to set up an efficient, structural CDC verification flow for all ten blocks.

Karl Pfalzer

After 20 years of engineering, AMCC’s Karl Pfalzer still finds inspiration in the verification and implementation puzzles he has to solve to deliver complex ICs.

Questa exceeds expectations; progress to formal

“The Questa CDC use model is great,” says Mr. Pfalzer. “It outshines the others in terms of showing where the problems are, helping organize that information, using familiar schematics and blocks, color-coding clock domains and crossings, and so forth—all of which help you iterate and successively refine.”

Mr. Pfalzer also looked into the formal capabilities of competitive tools. Again, he ended up coming back to Questa CDC, as the features they were looking for from the other vendors already existed in the Mentor tool.  Ultimately, Karl plans to use Questa CDC for top-level verification of the full network processor design. Furthermore, he would like to apply the tool earlier in the design flow, particularly to qualify IP from a CDC perspective.

For a problem like this you need excellent visualization techniques, and that’s where the Mentor CDC tool definitely shines above the rest.”

Karl Pfalzer, Chief Verification Engineer, AMCC

About AMCC

Founded in 1979, Applied Micro Circuits Corporation (AMCC) has been the market share leader in packet processors since the inception of the network processing industry. Its award-winning PowerPC® processors use best-in-class-technology and have achieved mass-market acceptance from major networking, storage, and consumer OEMs.  Company website:

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