Payments to a customer to not buy a competitor's product is a form of price fixing. Other Intel customers would then not know what the real market price was. They were therefore undermining AMD's opportunity without the market being able to take advantage of the price war between them.

Intel seems over-ripe for anti-trust action at this point. I think the government is codling them in all likelihood. This is not a technical issue, I suspect it is far more of Intel taking advantage of its strong political clout.