Engines of Our Ingenuity

No. 2802: ONE TRACK MIND

Andrew Boyd

Today, a one track mind. The University of Houstonís College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Playing music. Downloading pictures. Checking for viruses. Computers manage to do a lot of things at the same time. But thatís not exactly true. Theyíre really very single minded.

At the heart of all computers is a small device called the central processing unit, or CPU for short. CPUs are where all the decisions are made. At any given instant, the CPU can focus on exactly one activity.

They are, however, fast. They can switch from one task to the next so quickly that they appear to be doing several things at once. A fraction of a second here, a fraction of a second there. The formal name for this activity is multitasking. One of the important jobs performed by a computerís operating system is coordinating the many demands for the CPUís time. Every few milliseconds the operating system checks to see whatís waiting to get done, makes decisions about whatís most important, then makes the CPU available for the chosen task. Itís like a good secretary managing the flow of visitors into the office of a very important person.

black and white secretary photo

Sometimes visitors are allowed to barge their way in using a process known as an interrupt. When an interrupt arrives, the CPU sets everything aside and handles the interrupt. A keystroke, for example, generates an interrupt. ďHereís a capital GĒ arrives a keystroke impulse from the keyboard. The CPU quickly decides what to do with it then gets back to what it was doing before. Quite literally, a CPUís work is never done.

The means by which computers reckon is fascinating when you think about it. Humorous accusations aside, most humans can walk and chew gum at the same time. Computers canít. They walk a little, then chew a little, then walk a little more. And the whole computing endeavor depends on the CPU. Damage this tiny little device, and the entire computer ceases to function.

Doublemint Gum dated image

Thatís a far cry from how the human brain operates. There are regions of the brain that control functions like speech and language, but no exact location we can point to and say ďaha, thatís where words are interpreted.Ē Human thought is highly distributed.

The gameís changed a bit for computers in recent years. Theyíre now routinely designed with two, four, or even more CPUs. But individually the CPUs are still all alike: each can do one and only one thing at a time. Not exactly a one track mind, but not a highly evolved, highly distributed thinking machine either. Itís more like a committee of one track minds — one track minds of incredible speed and efficiency, but one track nonetheless.

[One Track Mind audio]

Iím Andy Boyd at the University of Houston, where weíre interested in the way inventive minds work.

(Theme music)


Notes and references:

For a related episode, see INSIDE THE MACHINE.

One Track Mind was written and recorded by the group Papa Roach.

The picture of Rose Conway, President Harry Trumanís Secretary, and the Doublemint Gum picture are from the Library of Congress.

This episode was first aired on June 7, 2012



The Engines of Our Ingenuity is Copyright © 1988-2012 by John H. Lienhard.