The set of instructions that is examined for simultaneous execution
is called the window.Each instruction in the window must be kept in
the processor,and the number of comparisons required every clock is
equal to the maximum completion rate times the window size times
the number of operands per instruction (typically 6 * 80 * 2), since
every pending instruction must look at every completing instruction.
Limitations on the Window Size and Maximum Issue Count.
Computer Architecture: A Quantitative Approach, Third Edition