Interplay of Failure Rate, Performance, and Test Cost in TCAM under Process Variations

As process variations grow with technology scaling, failure rates increase and are predicted to be so high as to render devices unusable for computing domain. In order to continue to benefit from scaling, three dimensions can be explored: increasing operational margins, testing, and the resilience of applications. The solutions in each dimension bring out different trade-offs in yield, failure rate, test cost, and performance. We use a ternary content-addressable memory (TCAM) as a case study to better understand these trade-offs. We develop two new delay tests for TCAMs, and a new method to estimate yield, failure rate, test cost, and performance of TCAM under process variations when various tests are used. Our results show that with little test overhead and negligible yield loss, our new tests can significantly decrease the failure rates of TCAMs shipped to customers.