No need to register your AMD processor. If it is an authentic AMD Processor in a Box (Original packaging) it will have an automatic 3 year Warranty.
When you open a AMD WARRANTY REQUEST, all you will need is Proof of Purchase (Receipt/Invoice), Date of Purchase, You were the one that purchased the Processor (Original Owner), Price amount of the purchase and the Processor Serial Number and Model number from either the AMD Box or from the imprinted information on the processor itself.
AMD can verify you have an authentic AMD Processor by it Serial Number and Model Number when you open a Warranty Request. But I believe you first must go through your Retailer Warranty before using AMD Warranty or after the original Retailer's warranty expires.