If you're after some bed-time reading, this will put you to sleep....
http://members.cox.net/lmcoon/salarycap.htm
This will answer any lingering query you might have with regard to the cap and the new collective bargaining agreement. Very good stuff.
The cap is based on BRI- basketball related income. A set percentage of projected league revenues minus adjustments is taken to determine the salary cap for each team. For the current year, negotiations for the new Collective Bargaining Agreement dictated a set figure of 49.5 million as supposed to the aforementioned percentage of BRI.