Paul, 'max pain', this is how I understand it:
(I will assume the reader basically knows how options work. Otherwise this will make no sense at all.)
Funds like to sell options and make money on the time premium, a nice strategy if you have enough money to make it work. So, for the funds, options that expire worthless are the best options of all!
For a set of options which expire on a given date, you can run a calculation on the outstanding call and put contracts to figure out the price at which the most options expire worthless, making the most time value profits for the funds. This is the 'max pain' number. If this number is near enough to the price of the stock then it may be profitable for the fund to trade shares of the stock to get it to close around this number. What they lose on the stock trades, they more than win on the option expiration.
IMO, a max pain of 12.5 would mean that no fund is going to try to manipulate AMD stock because of the huge losses they would take on the stock trades - if they short it down that far, then the short squeeze explosion would be very bad for them.