Agilex™ 7 F-Series and I-Series FPGA Memory Subsystem IP User Guide

ID 789389
Date 7/15/2024
Public
Document Table of Contents

3.1.1.1. Write Data Replication

To boost DDR performance, the memory-specific adaptor (MSA) can create multiple redundant copies of data, essentially breaking the RAM into multiple replicas.

This feature writes data to multiple banks and is best for applications that have a high ratio of reads to writes. Since there are multiple banks with data, the read access will have an open bank available and not have to wait for a bank charge process

For example, if the system has 8 GB of RAM and the MSA creates 4 copies of data, you will only have access to 2 GB. When a write operation arrives, the memory-specific adaptor converts it into a number of write request to all the copies; when a read operation arrives, the MSA decides which copy to read. When working with a multiple-reads workload, improved performance is realized by issuing reads to different copies and avoiding tRC and TFAW penalties. If there is sufficient memory bandwidth, the memory-specific adapter can perform one read access per clock cycle (the latency introduced is not critical, because DDR memory latencies are higher).

Lookup core IPs require write acknowledgement, which the DDR memory controller does not provide. The memory-specific adapter generates the acknowledgement internally, just before a burst write is committed.