The 610 faulting on NV condition codes is part of a journey of that bit of the instruction space from the original &quot;really never executed, ie NOP&quot; in the ARM1 (which just falls out of the implementation) through &quot;this is unpredictable&quot; (where UNDEF is a permitted implementation and helpful for flushing out stray applications relying on the old behaviour) until you get to the ARMv5 architecture, which uses the space for a collection of new instructions (which can&#x27;t be conditional). A whole sixteenth of the encoding space turns out to be just too precious to waste.