Many Users have mentioned that, even though, by overclocking your AMD Processor or GPU card voids the AMD Warranty that AMD wouldn't know it has been overclocked if the Users turned it in for RMA purposes. I suspect that AMD Engineers probably can tell if a Processor has been Overclocked. In the processor it could have a tiny file incorporated that shows whether it has been overclock or not. The GPU card may have something similar.
Many Users sometimes uses features/software that Overclock the processor or GPU card without realizing it will void the warranty. Many do it on purpose believing AMD has no way of knowing if they have overclocked AMD hardware.
From obvious physical damage from Overclocking, Can AMD Engineers determine if the Processor or GPU card was Overclock when sent in for RMA purposes?