Internal Error: Sub-system: VPR20KMAIN, File: /quartus/fitter/vpr20k/altera_arch_common/altera_arch_place_delay.c, Line: 3906 - Internal Error: Sub-system: VPR20KMAIN, File: /quartus/fitter/vpr20k/altera_arch_common/altera_arch_place_delay.c, Line: 3906 Description Due to a problem in the Quartus® Prime Pro edition software, you may see this internal error when compiling your design with physical synthesis enabled. Resolution To avoid this error, apply the following constraint in your .qsf (quartus settings file): set_global_assignment -name ALLOW_REGISTER_RETIMING OFF This problem is scheduled to be fixed in a future release of the Quartus Prime Pro edition software. Custom Fields values: ['novalue'] Troubleshooting FB: 401360; False ['novalue'] ['FPGA Dev Tools Quartus® Prime Software Pro'] novalue 16.0 ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']