> PMADDUBSW produces a word result which, in turns out, does not quite work. The problem is that multiplying unsigned by signed bytes means the individual produ

> PMADDUBSW produces a word result which, in turns out, does not quite work. The problem is that multiplying unsigned by signed bytes means the individual product terms are in range [-128*255, 128*255] = [-32640,32640]. Our result is supposed to be a signed word, which means its value range is [-32768,32767]. If the two individual products are either near the negative or positive end of the possible output range, the sum overflows. can someone explain this to me? isn't 32640 < 32767? how's this an overflow?