Editing Program counter (section)

== Consequences in machine architecture ==
Use of a PC that normally increments assumes that what a computer does is execute a usually linear sequence of instructions.  Such a PC is central to the [[von Neumann architecture]]. Thus programmers write a sequential [[control flow]] even for algorithms that do not have to be sequential.  The resulting “[[von Neumann bottleneck]]” led to research into [[parallel computing]],<ref name="Chambers_1984" /> including non-von Neumann or [[dataflow]] models that did not use a PC; for example, rather than specifying sequential steps, the high-level programmer might specify desired [[functional programming|function]] and the low-level programmer might specify this using [[combinatory logic]].

This research also led to ways to making conventional, PC-based, CPUs run faster, including:

* [[Pipeline (computing)|Pipelining]], in which different hardware in the CPU executes different phases of multiple instructions simultaneously.
* The [[very long instruction word]] (VLIW) architecture, where a single instruction can achieve multiple effects.
* Techniques to predict [[out-of-order execution]] and prepare subsequent instructions for execution outside the regular sequence.