The message "Process Synthesis Failed" is generated by Project Navigator in the event of an error code being returned.
If XST is not issuing any messages with the reason, the following are possible solutions:
- "Cleanup Project Files" and remove the _xdb folder.
- Re-create the project.
- Try running ISE 32bit.
- Run XST command line using the information in the Command Line Log File (.cmd_log) in the project directory.
- If there are IP cores or NGC/EDIF netlists used in the project, try disabling the "-read_cores" option in XST Process Properties.
- If an NGC netlist is actually generated from XST in the project directory, you can create another project for Implementation with this NGC as top level and the UCF file(s).
Alternatively you can right click Synthesis - XST , force process up-to-date, then continue to run implementation.
- There is a known issue where the license checking of a Xylon IP causes XST crashes in ISE 14.6 and 14.7.
A patch to resolve this issue is provided in (Xilinx Answer 59851)
If none of the above solutions help, please refer to (Xilinx Answer 40377).
The debug steps for XST internal/fatal errors can also be used for this issue.
For more information on running XST command line and XST options, please refer to UG687.