A couple of days ago, there were curious reports about AMD forbidding the use of third-party processor coolers. Basically, a support page on the firm's website stated that in order not to void the warranty, users could not use a different heatsink/fan other than the one provided in the processor-in-a-box (PIB). It was a weird statement, but it was right there on the official AMD website.
After inquiries, AMD has updated the page with the following message:
Is the warranty for my AMD Processor-in-a-Box (PIB) still valid if I use a different heatsink/fan (HSF) other than the one provided in the PIB?
Yes, provided that the selected HSF, when properly installed and used, supports operation of the AMD processor in conformance with AMD’s publicly available specifications. Use of HSF solutions determined by AMD as incapable of such performance or which are determined to have contributed to the failure of the processor shall invalidate the warranty.
So basically, the new statement is what common sense dictates. You can use a different cooler without voiding your warranty, but you need to ensure the third-party cooler is beefy enough to handle the heat output of your CPU.