3.2. Processing Power

Often known as CPU power, CPU cycles, and various other names, processing power is the ability of a computer to manipulate data. Processing power varies with the architecture (and clock speed) of the CPU -- usually CPUs with higher clock speeds and those supporting larger word sizes have more processing power than slower CPUs supporting smaller word sizes.

3.2.1. Facts About Processing Power

Here are the two main facts about processing power that you should keep in mind:
  • Processing power is fixed
  • Processing power cannot be stored
Processing power is fixed, in that the CPU can only go so fast. For example, if you need to add two numbers together (an operation that takes only one machine instruction on most architectures), a particular CPU can do it at one speed, and one speed only. With few exceptions, it is not even possible to slow the rate at which a CPU processes instructions, much less increase it.
Processing power is also fixed in another way: it is finite. That is, there are limits to the types of CPUs that can be plugged into any given computer. Some systems are capable of supporting a wide range of CPUs of differing speeds, while others may not be upgradeable at all[10].
Processing power cannot be stored for later use. In other words, if a CPU can process 100 million instructions in one second, one second of idle time equals 100 million instructions worth of processing that have been wasted.
If we take these facts and examine them from a slightly different perspective, a CPU "produces" a stream of executed instructions at a fixed rate. And if the CPU "produces" executed instructions, that means that something else must "consume" them. The next section defines these consumers.


[10] This situation leads to what is humorously termed as a forklift upgrade, which means a complete replacement of a computer.