Why is my Low Latency 40-Gbps Ethernet IP Core generating 66-byte flow control packets when Flow Control Mode is set to “Priority-based flow control” and the Number of PFC queues set to “8”?

Description

Due to a problem in the Quartus® Prime Software, the Low Latency 40-Gbps Ethernet IP Core with “Priority-based flow control” enabled and the number of PFC queues set to “8” will generate 66-byte flow control packets. 

Resolution

To work around this problem, do not set the number of PFC queues to “8” in the GUI. Any other number of PFC queues is sufficient.