Hi Weichun,
You are right, we dont have C6657 Cycle accurate simulator config.
Can you kindly go though the user guide for Keystone simulators at http://processors.wiki.ti.com/index.php/TCI6616/C6670/TCI6608/C6678/TCI6618_Device_simulator_User_Guide
that details the list of configurations and defines what we mean by cycle approximate simulator in terms of validation and scope. Please get back with any more questions you may have.
regards,
Sheshadri