> Is it a correct mental model then to think about control unit being a logical or "distributed" unit(right side of diagram) instead of a monolithic unit(the le

> Is it a correct mental model then to think about control unit being a logical or "distributed" unit(right side of diagram) instead of a monolithic unit(the left side of diagram)? That is a somewhat reasonable interpretation. Just keep in mind that both diagrams are massive simplifications of the actual reality (i.e., the left side diagram likely had a more dispersed control system than the block diagram would lead one to believe). > I'm guessing this "reservation station/reorder buffer variant" of control unit is the predominant one in use in CISC chips these days? It is/has been a popular model (first introduced by IBM in the 360/91 mainframe circa 1967 -- R.M. Tomasulo, "An Efficient Algorithm for Exploiting Multiple Arithmetic Units, https://www.cs.virginia.edu/~evans/greatworks/tomasulo.pdf https://www.cs.virginia.edu/~evans/greatworks/tomasulo.pdf) for many designs over the years. As for predominant in CISC chips, that really depends upon what current Intel/AMD CPU's are doing internally, and I've not kept up with their most recent offering's internal designs.