No-Fit in DDR3 Interfaces Due to mem_ck Assignments

Description

This problem affects DDR3 products.

A DDR3 memory interface that compiled successfully in version 11.1 of the Quartus II software may encounter a no-fit in version 12.0 if mem_ck is assigned to a differential pin pair where p is inside a DQS group and n is outside the DQS group.

Resolution

The workaround for this issue is as follows:

1. Open the file xxx_addr_cmd_pads.v in a text editor.
2. Search for the localparam USE_ADDR_CMD_CPS_FOR_MEM_CK and set its value to true.

This issue will be fixed in a future version.