CRPR_AppNote_v1.4

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The following are the main points of this application note.  Each point is explained in more detail in the
following article.

What is CRPR?
An explanation of what Clock Reconvergence Pessimism is and how it is
calculated.
Advantages of PT’s CRP calculation over other methods
PrimeTime’s original implementation of CRPR was of the “Path based” type.  This
technique has inherent limitations.  This section explains the relative merits of path
based CRP calculations versus graph based approaches, and how it can miss critical
timing paths.  All versions of  PrimeTime after 2001.08 utilize a graph based CRP
solution.
CRPR Command and variable overview
An overview of all the applicable CRPR commands and their usage.
Report_timing & report_crpr may show slightly different CRP values.
The value of CRP reported by report_timing may be less than the value of CRP
reported by report_crpr, with a lower bound set by the CRPR variable <var name>
(see variables and commands below).
CRPR & Latches.   
CRPR & SI analysis.
An explanation of CRPR calculation with SI analysis.
CRPR & IR drop.
An explanation of how CRPR works with the multi-voltage flow in PrimeTime T-
2002.09 is given, including an explanation of how CRP removal will automatically
and accurately account for delay and slew differences due to annotated cell rail
voltage values in the CRP calculation, as part of the IR drop flow.

CRPR & Multiplexed Clocks.
The support of related and combined clocking structures is explained for the V-2003.12 release

CPU & Memory Performance.
Performance and memory improvements are explained and discussed for the V2003.12 release

Understanding calculation pessimism introduced by the CRPR threshold
Performance and memory improvements are explained and discussed for the V2003.12 release

Known Issues

References