In some cases it is safe to ignore this Switching Limit Error.
This only applies if there is no intention to read back from the BRAM modules.
These situations occur when using the SEM IP core and a POST_CRC process is going to be executed with the ICAP.
The speed files include the Switching Limitation for each component, however, they do not include the differences for ICAP module without read back from BRAM.
As a result, the tool uses the worse case scenario: 20 MHz.
Because there are no future plans for S6 devices, those speed files will not be updated.