Processing Power; Facts About Processing Power; Consumers Of Processing Power - Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

34
For example, consider a SCSI adapter that is connected to a PCI bus. If there are performance problems
with SCSI disk I/O, it might be the result of a poorly-performing SCSI adapter, even though the SCSI
and PCI buses themselves are nowhere near their bandwidth capabilities.

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
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.

3.2.2. Consumers of Processing Power

There are two main consumers of processing power:
Applications
•
The operating system itself
•
3.2.2.1. Applications
The most obvious consumers of processing power are the applications and programs you want the
computer to run for you. From a spreadsheet to a database, applications are the reason you have a
computer.
2. This situation leads to what is humorously termed as a forklift upgrade, which means a complete replacement
of a computer.
Chapter 3. Bandwidth and Processing Power
2 .