CPU characteristics and their impact on performance
Introduction
Not all CPUs are equal! There are a number of reasons for this.
Materials
Just like cars or phones or anything else you buy, CPUs are made up of materials and some materials have a better quality than others. The quality of materials that make up a processor will affect the reliability, speed and performance of a CPU. A component in a CPU that is very slow and poorly made will slow down the overall performance of the CPU.
Clock speed
CPUs have a clock inside them, ticking away. Instructions are carried out each time a tick of the clock happens. Some instructions only need one clock tick whereas others will need more than one. The faster the clock, the more instructions you can carry out in any second. A typical clock these days might be 4 Gigahertz or 4 billion ticks a second, for example.
Cache
Although CPUs fetch instructions from RAM, there is another place in can get instructions from, called 'cache'. Cache is just like RAM but much faster to read from and write to compared to RAM. The computer cleverly puts data into cache that it needs again and again. It is a lot quicker for the CPU to get data from cache than RAM. The more cache a computer has, the better the CPU will perform.
Cores
A CPU traditionally had one 'core' but processors these days might be dual-core or quad-core, for example. A core is actually a processor with its own cache. So a dual-core CPU has not one but two processors. A quad core CPU has four processors. Two brains (or four brains) are better than one! Each brain can be working on different parts of a program at the same time and so this speeds up the overall CPU's performance.
Word size
Processors work on instructions and data, which it has fetched from RAM. These instructions and data are in binary. If a processor can work on this number: 0111 0011 1111 1111 then it is said to be a 16 bit processor. But if a processor can work on 32 bits (a 32 bit processor) in one go or even on 64 bits (a 64 bit processor) in one go then it can work on more data and more instructions for every tick of the CPU's clock. The word size simply refers to the number of a bits a CPU can work on in one go. The bigger the word size, the better the CPU's performance will be.