what entity are you under? PM is a US concept and in markets like HK, risk based margin is the norm and very similar to PM.
This is on the TDA website. Looks like Charles Schwab needs TD to offer PMA. Does that concern you if you have an account here? "However, if you're interested in trading futures and forex products, or using portfolio margin, we recommend that you open a TD Ameritrade account for the best experience."
You said they give 60% of your total as PM - so for 100k portfolio value - u get 60k portfolio margin ( can we also call it options buying power?) Do we have to pay interest on this 60k portfolio margin they provide?