Analysis of testing methodologies for custom designs in PowerPC/sup TM/ microprocessor

Custom circuits, in contrast to those synthesized by automatic tools, are manually designed blocks of which performance is critical to the full chip operation. Testing these blocks represents a major DFT challenge and hence, a crucial time-to-market factor in microprocessor design flow. This paper compares three industry-adopted methodologies for testing custom blocks. Pros and cons are analyzed and discussed based on factors such as stability of the methodologies, resulting sizes of gate-level models, ATPG process, and testing quality in terms of non-target defect detection. Experience and results from a recent PowerPC microprocessor are reported.