1. In a processor for processing instructions which operate on a plurality of data elements packed into an operand, a method of sorting numerical values into minima and maxima groupings, comprising the steps of: comparing data elements of a first source operand to corresponding data elements of a second source operand by performing a comparison operation, wherein said data elements of said two source operands represent numerical values, in order to determine a numerical relationship between each pair of said corresponding data elements of said two source operands; generating a mask operand which has data elements corresponding to a result of said numerical relationship; performing a first logical operation, which is an exclusive-OR operation, on said corresponding data elements of said two source operands in order to generate a first interim operand in which its data elements correspond to results of said first logical operation; performing a second logical operation on corresponding data elements of said first interim operand and said mask operand in order to generate a second interim operand in which a value of each of its data elements corresponds to either a corresponding data element from said first interim operand or a masked value from said mask operand; performing a third logical operation, which is an exclusive-OR operation, on corresponding data elements of said second interim operand and said first source operand to generate a minima operand in which its data elements represent lesser or equal values from each pair of values compared in said comparing step of said two source operands; performing a fourth logical operation, which is an exclusive-OR operation, on corresponding data elements of said second interim operand and said second source operand to generate a maxima operand having its data elements represent greater or equal values from each pair of values compared in said comparing step of said two source operands.