Difference between AOCV and POCV?

[srshankar]

Hello,

Could somebody explain how POCV is exactly different from AOCV ?? And the cons of AOCV ..



Thanks in advance.

 

[rca]

from Synopsys:

Advanced on-chip variation (AOCV) analysis reduces unnecessary pessimism by taking the design methodology and fabrication process variation into account. AOCV determines derating factors based on metrics of path logic depth and the physical distance traversed by a particular path. A longer path that has more gates tends to have less total variation because the random variations from gate to gate tend to cancel each other out. A path that spans a larger physical distance across the chip tends to have larger systematic variations. AOCV is less pessimistic than a traditional OCV analysis, which relies on constant derating factors that do not take path-specific metrics into account. 

The AOCV analysis determines path-depth and location-based bounding box metrics to calculate a context-specific AOCV derating factor to apply to a path, replacing the use of a constant derating factor. 

AOCV analysis works with all other PrimeTime features and affects all reporting commands. This solution works in both the Standard Delay Format (SDF)-based and the delay calculation based flows.

PrimeTime ADV parametric on-chip variation (POCV) models the delay of an instance as a function of a variable that is specific to the instance. That is, the instance delay is parameterized as a function of the unique delay variable for the instance. POCV provides the following: 

•Statistical single-parameter derating for random variations 

•Single input format and characterization source for both AOCV and POCV table data 

•Nonstatistical timing reports

•Limited statistical reporting (mean, sigma) for timing paths 

•Compatibility with existing PrimeTime functionality, except PrimeTime VX 

Compared to AOCV, POCV provides 

•Reduced pessimism gap between graph-based analysis and path-based analysis 

•Less overhead for incremental timing analysis

 

[srshankar]

Thanq rca, but could u explain in simple words why we are exactly going for POCV from AOCV (I knw to reduce pessimsm is one reasn) ?? What are the problems with AOCV and how POCV addressing them??