1. A method of checking the integrity of one or more input vectors to a digital hardware block, the method comprising: identifying a set of known bad input vectors for the digital hardware block, wherein the known bad input vectors are vectors that are known to trigger a hardware fault within the digital hardware block when input to the digital hardware block; and training checking circuitry to selectively classify future input vectors to the digital hardware block as either good or not good, using the set of known bad input vectors, wherein good input vectors are processed by the digital hardware block and not good input vectors are processed by a software work-around, wherein the software work-around performs a same task as the digital hardware block, and wherein the checking circuitry classifies a given input vector as good or not good in less than 60 ns.