After PAR completes, there is a "timing.twr" file in the directory that does not match timing with the Timing Summary of the PAR report, nor the report listed in TRCE.
What is the meaning of this report and is the timing number valid?
The "timing.twr" file is generated by PAR to track intermediate timing results, and should be disregarded when the design completes implementation.
Beginning with ISE revision 9.1i, a new feature in PAR was created called SmartPreview.
SmartPreview allows the user to access intermediate timing results while a design is still routing (accessed with Ctrl-C).
To do this, PAR generates a "timing.twr" file which is updated while PAR is still running.
The problem is that the file is not updated with the final timing results when routing is completed, leading to a mismatch with other timing reports.
This issue is scheduled to be fixed in ISE revision 10.1i.