Why is the Mailbox Client Intel® FPGA IP command returning 0x3FF when multiple instances of this IP are used in Intel® Stratix® 10 and all Intel Agilex® devices?

Description

Due to a problem in the Intel® Quartus® Prime Pro Edition Software version 20.3, when multiple instances of the Mailbox Client Intel® FPGA IP are trying to perform QSPI write operations at the same time in Intel® Stratix® 10 or all Intel Agilex® devices, the IP command returns 0x3FF instead of 0x1FF.

Resolution

To prevent this error, do not perform QSPI write operations at the same time with multiple Mailbox Client Intel® FPGA IP.

This problem is fixed starting with the Intel Quartus Prime Pro Edition Software version 20.4.