title: Default cache parameters, how to change, limitation and more
body: <p>I am new to rocket chip generator and still learning. First thing I want to know is how to parameterize l1 d cache. I did some research but it seems the info is not up to date. For example, in src/main/scala/config.scala, there is no d cache parameters defined as mentioned in README. Some people mentioned coreplex/config.scala but I couldnt find it either. 
  Will someone please let me know where are the default parameter defined and how to change them? Also, where is the tinycore, bigcore and other predefined core defined?</p>