MentorGraphics ModelSim SE 6.6d error: Fatal: Unexpected signal: 11. - MentorGraphics ModelSim SE 6.6d error: Fatal: Unexpected signal: 11. Description During simulation of a Qsys-generated VHDL design that includes DDR2 or DDR3 external memory cores with ALTMEMPHY, the 64-bit version of Mentor Graphics ModelSim SE 6.6d may issue a fatal error similar to the following: #**Note: (vsim-3812) Design is being optimized... #**Fatal: Unexpected signal: 11. Resolution Use the 32-bit version of Mentor Graphics ModelSim SE 6.6d or use the -novopt option with the vsim command. Custom Fields values: ['novalue'] Troubleshooting novalue True ['novalue'] ['FPGA Dev Tools Quartus II Software'] novalue 11.0 ['Arria® II FPGAs'] ['novalue'] ['novalue'] ['novalue']