Hello Dr. Architecture:
The best source for the answer to your question is the graduate programs to which you are applying. First, check their website for requirements, etc. If you need more details, contact them directly.
Another source is the book - Portfolio Design and the website by the same name - http://www.portfoliodesign.com both by Harold Linton. Both the book and the website provides you some insight on the process of generating a portfolio.
As you shifting from CE to architecture, you would not be expected to include architectural work, but rather creative work of different media - drawing, painting, etc.