Due to a problem in the Intel® Quartus® Prime Pro Edition Software version 20.1, the last burst of read data may not return promptly in Read Modify Write (RMW) mode.
The read command gets executed whenever there is a new command, a refresh, or an auto-precharge. This last read burst that has been delayed may cause reduced efficiency.
To work around this problem, ensure refresh is executed periodically per DDR4 specification if the User-Refresh option is turned ON, or turn ON the Enable User Auto-precharge option and execute the auto-precharge command for all transactions.
Refer to the External Memory Interfaces Intel® Stratix® 10 FPGA IP User Guide for more details.
This problem is fixed starting with the Intel® Quartus® Prime Pro Edition Software version 20.2.