Certainly it is. There are traditionally two kinds of single-stepping: Single-clock-cycle (implemented in hardware): the processor does whatever it normally does on one one clock cycle every time you "press the button". A superscalar processor can do that just as well as any other processor, though it will typically be executing part or all of several instructions every time you give it a clock. Single-instruction (can be hardware on some systems, but more commonly implemented in software): my debugger still does that just fine, even on the latest superscalar processors. I use it all the time. It would be pretty tough to debug software if one couldn't do that.