Why do I observe unexpected staircase/plateau effects on Arria 10 output signals?

Description

Due to a known issue in the Quartus® Prime software versions 15.0 to 15.1.2, you may observe unexpected voltage levels and rise/fall times, when compared to IBIS/HSPICE simulation, on Arria® 10 output signals.  

This is due to incorrect drive strength settings being applied in the generated SOF file compared to the user defined settings.

Resolution

To work around this problem in Quartus Prime software versions 15.0 to 15.1.2, please contact mySupport to request a patch.

This problem is scheduled to be fixed in a future release of the Quartus Prime software.