John,

Is two's-complement addition really faster, or is does it just require fewer transistors (reuse those for addition when doing subtraction)? At one time minimizing transistors was very important, but today the question is usually how can you best use the available ones.

Is it time to reevaluate the choice between one's complement and two's complement arithmetic? A one's complementation (nice verb) is a simple XOR operation and does not require a bit flip to be propogated through an entire byte value. This would mean no spare bits left over to crash to the floor. Perhaps the noise associated with these bits was not as significant years ago when the processors were several orders of magnitude slower.