Why the default value of clock frequency on evmDM6446 is 576Mhz?

Where are you seeing 576 Mhz?  I cannot seem to find this reference.

You make a good point, even in BIOS 3.33.03 the TCI file for DM6446 has the frequency set at 576MHz, I suspect this is an error in the TCI file, as you suggest the typical frequency is 594MHz (22x multiplier with 27Mhz input clock). In any case this is an easy fix, just change the value to whatever frequency you are actually using. This should only have an impact on the clock module, so for example if you were using periodic functions (PRD) they would be running slightly off if this was not set correctly.

thank you very much!