On 7 September 2010 18:08, Steve Smith <[email protected]> wrote: > On 9/7/2010 1:26, Robert A. Rosenberg wrote:
>> The result is ONLY the same if the original value is positive (high >> bit = 0). If it is negative (high bit = 1) then the result is wrong >> since it results in a positive intermediate value being subtracted >> from the signed value and a negative intermediate value being added >> to the signed value. >> > John is correct. The results of A and AL are always the same, except > for the condition code. That's what makes 2s-complement so cool. It's also how "classic" (base & displacement) addressing arithmetic, which we all know deals only with unsigned values, can subtract. Tony H.
