How common characteristics of CPUs affect their performance
Not all processors are equal!
Similar specification processors perform differently. There are a number of reasons for this.
- The materials the processor is made from. Different processors, like any product, are made using different materials and different qualities of materials. There are 'good' quality materials and not-so-good ones! The materials used in a processor will affect the reliability, speed and performance of that processor. Importantly, the speed of the slowest component might slow right down an otherwise fast CPU.
- Clock speed. Another reason why different processors perform differently is clock speed. Every computer has a 'clock'. This is a crystal that vibrates, generating 'pulses' that are used to control how the different components of a computer system work together. If you have a 800Mhz machine, it means the system clock is generating approximately 800 million pulses every second! The faster the clock, the more fetch-decode-execute cycles the CPU can perform in a second, and (very broadly) the faster your programs should go! (There are lots of other factors that may mean this is not the case, however).
- 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.
- 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.
- Word size. An important characteristic of a processor is its word size. This is the number of bits that the CPU can work with in any one clock cycle. The more bits it can work with in one clock cycle, the faster the computer will go. The early commercial computers like the Spectrum ZX were 8-bit computers (in another words, the processor could work on 8 bits of data at a time). Things have moved on since the early 1980s and you are likely to be using either a 32-bit computer or a 64-bit computer now. No doubt we will all be buying 128-bit computers in the near future!