Dwarf

This is nothing new. When chip dies are created (and I am talking about CPUs as well as GPUs from Intel, AMD, NVidia and other manufacturers), some will work correctly as intended, others will fail to work at the intended speed but will work at a reduced speed, and others will not work at all. At the start of production of a new chip, the number of chips that do not work at all may be as high as 10% and those that do work as intended may be as low as 20%, leaving the remainder which do work, albeit at a lower speed. As the production cycle progresses, the quality of chip production increases and the number of chips that do not work at all falls dramatically. In addition, the number of chips produced that can run at the intended speed rises. Not all of these chips will be marketed as such, and some will actually be marketed as a lower range chip. This explains why some chips are good overclockers - they are actually higher range chips sold as a lower range model. Despite careful selection and testing, it is possible for defective chips to make their way to the consumer where they will work for a period of time and then fail. Unfortunately, it is impossible to say whether a chip that has passed testing will remain in working order or will, at some point in the future, fail for some reason or other. The real enemy of chips is HEAT, therefore it is essential to ensure that heatsinks and fans of the correct ratings are correctly installed and maintained to minimise its effects.
Dwarf