Device Family: Intel® Arria® 10 GT, Intel® Arria® 10 GX, Intel® Arria® 10 SX, Arria® V GT, Arria® V GX, Arria® V GZ, Arria® V ST, Arria® V SX, Cyclone® V GT, Cyclone® V GX, Cyclone® V SE, Cyclone® V ST, Cyclone® V SX, Stratix® V GS, Stratix® V GT, Stratix® V GX

Type: Answers

Area: Intellectual Property

IP Product: PCI Express 1/2/4/8 Lanes (x8)

RX buffer credit allocation - performance for received requests" (rxbuffer_rxreq_hwtcl) " is out of range: "Minimum", "Low", "Balanced"


This error message is displayed when opening a Quartus® II v13.1.4 Qsys system in Quartus II v14.0 or later, if the system has an Altera® Avalon®-MM Hard IP for PCI Express® with High or Maximum RX Buffer Credit Allocation chosen.

In addition, when parameterizing the Avalon-MM Hard IP for PCI Express in Quartus II v14.0 or later, the High and Maximum settings for the Rx Buffer Credit Allocation are not available.


Altera found performance issues with the High and Maximum settings in the Avalon-MM variants. Consequently, these settings have been removed for Arria® V GZ, Arria 10 and Stratix® V devices from Quartus II software version 14.0.

These same parameters are scheduled to be removed for Avalon-MM variants in Arria V and Cyclone® V devices in a future software release.

This change will be reflected in a future version of the user guides.