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 (or equivalent hardware that serves the same purpose) 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, 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 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:
- 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.
Read more about this topic: Program Counter
Famous quotes containing the words consequences, machine and/or architecture:
“The horror of Gandhi’s murder lies not in the political motives behind it or in its consequences for Indian policy or for the future of non-violence; the horror lies simply in the fact that any man could look into the face of this extraordinary person and deliberately pull a trigger.”
—Mary McCarthy (1912–1989)
“But a man must keep an eye on his servants, if he would not have them rule him. Man is a shrewd inventor, and is ever taking the hint of a new machine from his own structure, adapting some secret of his own anatomy in iron, wood, and leather, to some required function in the work of the world. But it is found that the machine unmans the user. What he gains in making cloth, he loses in general power.”
—Ralph Waldo Emerson (1803–1882)
“Polarized light showed the secret architecture of bodies; and when the second-sight of the mind is opened, now one color or form or gesture, and now another, has a pungency, as if a more interior ray had been emitted, disclosing its deep holdings in the frame of things.”
—Ralph Waldo Emerson (1803–1882)