External Memory Interfaces Intel® Agilex™ FPGA IP User Guide

ID 683216
Date 1/31/2022

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10.4.7. Series of Reads or Writes

Performing a series of reads or writes from the same bank and row increases controller efficiency.

For best performance, minimize random reads and random writes. When you perform reads and writes to random locations, the operations require row and bank changes. To change banks, the controller must precharge the previous bank and activate the row in the new bank. Even if you change the row in the same bank, the controller has to close the bank (precharge) and reopen it again just to open a new row (activate). Because of the precharge and activate commands, efficiency can decrease by as much as 3–15%, as the controller needs more time to issue a read or write.

If you must perform a random read or write, use additive latency and bank interleaving to increase efficiency.

Controller efficiency depends on the method of data transfer between the memory device and the FPGA, the memory standards specified by the memory device vendor, and the type of memory controller.