This internal error may occur in the Quartus® II software version 4.1 SP2 when you compile your design targetting ACEX® 1K or FLEX 10K® devices.
You may be able to avoid the error with the following workaround:
- In the Analysis & Synthesis Settings page of the Settings dialog box (Assignments menu), select Speed as the Optimization Technique.
- In the Fitter Settings page of the Settings dialog box (Assignments menu), click More Settings.
- In the More Fitter Settings dialog box, ensure that Auto Packed Registers is set to Off.