WARNING: Attempting to read from uninitialized location

Description

You may experience the above warning when running a dual-rank DDR3 simulation.

This warning occurs during the memory initialization and calibration process. Uninitialized reads occur as the sequencer performs dummy reads to switch between shadow registers. The dummy read operations no longer occur after the memory calibration process is complete. 

Resolution

These warnings are harmless and should be ignored. The warnings don't occur in single-rank cases because shadow registers are disabled in those designs.