* The CLV (Clear Overflow Flag) instruction exist but not the SEV (Set Overflow Flag) instruction.
* The NOP instruction takes 2 full-cycles. This is the minimum amount of cycles an instruction can take. It is necessary because , while the instruction itself does nothing, it still has to increment the 16-bit PC register.
* The alternate NOPs are not created equal. Some have one- or two-byte operands (which they don't do anything with), and they take different amounts of time to execute.