NOR (NOT OR)

NOR X-form
nor RA,RS,RB (Rc=0)
nor. RA,RS,RB (Rc=1)

RA <-  ¬((RS) | (RB))
The contents of register RS are ORed with the contents
of register RB and the complemented result is placed
into register RA.

Special Registers Altered:
CR0 (if Rc=1)

Extended Mnemonics:
Example of extended mnemonics for NOR

Extended: Equivalent to:
NOT Rx,Ry   <=> NOR Rx,Ry,Ry

Please  NOTE here there is no logical NOT instruction on PPC architecture. Instead, we have this alias of nor Rx, Ry, Ry, which is actually equivalent to NOT Rx, Ry. But physically, there is no NOT hard instruction on PPC architecture, just NOR.