I ran PAR on the same design files job on two different platforms (Linux 64 and WinXP x64), and I get different results. Why does this occur, and can I trust the results?
All platforms should produce the same results with the same input files, same software revision, and same options. When this does not occur in PAR, the difference is often due to a subtle difference in a software function that creates a different, but equally valid result, because of order of processing differences. For example, a sorting function can produce different results and, consequently, a different order of processing. This difference is similar to running PAR with different Cost Tables.
Xilinx has observed a case in which WinXP x64 produces different results compared to other platforms. This problem is currently being investigated with an expectation of being fixed in 9.1i SP1, which is scheduled for early 2007.