I had said earlier that overflow is carry from the penultimate bits into the sign bit. But that isn't accurate. That's true for an adding positive numbers. But when adding two negative numbers, this carry would not mean an overflow. Rather this is the proper definition: When adding two numbers of the same sign, there is an overflow if the sum does not have the same sign.
What might be the most efficient way to work that into an adder in hardware? What about subtraction? Subtraction is the same as adding the negative of the subtrahend. However, in hardware, we don't first change the sign of the subtrahend and then add, because it is more efficient to use an optimized addsub macro. Therefore we can't integrate overflow into the addsub in quite the same way. -- Timothy Normand Miller http://www.cse.ohio-state.edu/~millerti Open Graphics Project _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
