AN 829: PCI Express* Avalon® -MM DMA Reference Design

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ID 683554
Date 6/11/2018
Public
Document Table of Contents
Document Table of Contents x
1. AN 829: PCI Express* Avalon® -MM DMA Reference Design
1. AN 829: PCI Express* Avalon® -MM DMA Reference Design x
1.1. Introduction 1.2. Working with the Reference Design 1.3. Understanding PCI Express Throughput 1.4. Document Revision History for AN 829: PCI Express* Avalon® -MM DMA Reference Design
1.1. Introduction x
1.1.1. DMA Reference Design Hardware and Software Requirements 1.1.2. Avalon® -MM DMA Bridge Module Descriptions
1.2. Working with the Reference Design x
1.2.1. Project Hierarchy 1.2.2. Parameter Settings for PCI Express Hard IP Variations 1.2.3. PCIe* Avalon® -MM DMA Reference Design Platform Designer Systems 1.2.4. DMA Procedure Steps 1.2.5. Setting Up the Hardware 1.2.6. Programming the Intel® Cyclone® 10 GX FPGA Oscillator 1.2.7. Installing the DMA Test Driver and Running the Linux DMA Software
1.3. Understanding PCI Express Throughput x
1.3.1. Throughput for Posted Writes 1.3.2. Throughput for Reads 1.3.3. Throughput Differences for On-Chip and External Memory
1.3.1. Throughput for Posted Writes x
1.3.1.1. Specifying the Maximum Payload Size
1.3.2. Throughput for Reads x
1.3.2.1. Understanding Throughput Measurement
1. AN 829: PCI Express* Avalon® -MM DMA Reference Design

1.3.3. Throughput Differences for On-Chip and External Memory

This reference design provides a choice between on-chip memory implemented in the FPGA fabric and external memory available on the PCB. The on-chip memory supports separate read and write ports. Consequently, this memory supports simultaneous read and the write DMAs.

The external memory supports a single port. Consequently, the external memory does not support simultaneous read DMA and write DMA accesses. In addition, the latency of external memory is higher than the latency of on-chip memory. These two differences between the on-chip and external memory result in lower throughput for the external memory implementation.

To compare the throughput for on-chip and external memory, select command 7 for consecutive runs to switch between on-chip and external memory.

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