Question

Explain from your own words the different factors affecting the processing speed of CPU.

Answer 1

Different factors affecting the processing speed of CPU:

        Being the brain of the computer, the CPU plays a very important role in determining the performance of the system. It is one of the most important component in a computer system. Its task is to take care of all the data calculation and make sure they are processed in the fastest time possible.

It is easy to think that the speed of the CPU is directly link to the performance of the CPU. This is only true to a certain extent. A CPU with fast speed will not be efficient if it has only a limited data to process. To achieve maximum efficiency, the hardware (especially the hard drive and memory) that are linked to the CPU must supply data as fast as the CPU speed. Failure to do this will result in a lagging computer, regardless how fast the CPU is.

1. CPU Clock Speed

The operating frequency of the CPU (also known as the clock speed) determines how fast it can process instruction.

The speed is measured in terms of Hertz, and it is usually lies in the megaHertz (MHz) or gigaHertz (GHz) range. A megaHertz means that the CPU can process one million instruction per second whereas a gigahertz CPU has the capability to process one billion instructions per second. In today technology, all CPUs run in the gigahertz range and you seldom see CPU with speed in the MHz range anymore.

Theoretically, a 500 MHz CPU is six times slower than a 3 GHz CPU and a 3.6 GHz CPU is faster than a 3 GHz or a 3.4 GHz CPU. In general, the higher the frequency of a CPU, the faster the speed of the computer.

2. Cache

Remember we mentioned above that for the CPU to work at its maximum efficiency, the data transfer from the other hardware must be as fast as its speed. The purpose of a cache is to ensure this smooth and fast transition of data transfer from the hardware to the CPU.

To understand the importance of a cache, it is necessary to understand how the whole process works. The main bulk of information comes from the hard drive. When an application is requested, the motherboard will fetch the required information from the hard drive and deliver it to the CPU for processing.

Since the hard drive processing speed is much slower than the CPU, data transfer often takes a long time. To speed thing up, the RAM is used to store temporary information from the hard drive. Instead of heading straight to the hard drive, the motherboard now checks and retrieves the data from the RAM. Only when the required information is not found in the RAM then will the motherboard go to the hard drive.

As CPU speed increased to the point where the RAM is no longer able to catch up, the transferring of information again become a serious problem. To solve this issue, a cache, which was effectively a small and extremely fast memory, was added to the processor to store immediate instruction from the RAM. Since the cache runs at the same speed of the CPU, it can rapidly provide information to the CPU at the shortest time without any lag.

3. Multi-Core

In the past, if you want to get a faster computer, you have to get a faster CPU. Today, this is only partially true. The reason being, CPU speed can’t increase forever. There is limitation as to how fast the transistors can run. When it reaches a plateau, you won’t be able to increase the speed anymore.

To tackle this problem, CPU manufacturers adopted a multi-core technology, which literally means putting multiple cores in a CPU chip. While increasing the CPU speed resulted in faster data calculation, putting more cores in a chip resulted in more work done at the same time.

4. Word length

This word length is the word length of a CPU . This is the number of bits a CPU can process simultaneously. For example a 32-bit processor is faster than a 16 bit processor because it has a wider word length. A typical computer system word length is normally between 32 and 64 bits.

Here are three examples of how the CPU clock speed and word length can vary:

• The 8088 processor has a clock speed of 4.77 MHz and has an 8-bit word length.
• The 80486 has a clock speed of 50 to 80 MHz and has a word length of 32 bits.
• The Pentium 4 as a clock speed of 1.5 gigahertz to 3.2 gigahertz and has a word length of 64 bits.

5. Address Bus Width

The address bus width is the width of the address bus and determines the maximum amount of addressable locations. For example if you have an address bus of 8 bits, this means that you can have 256 addresses. These addresses or memory locations will be numbered 0 to 255.

Of course, the wider your address bus, the larger the memory that can be accessed.

6. Data Bus Width

The Data bus width is the number of bits that can be transferred simultaneously from one device to another. Usually the data bus is the same size as the address bus but not always. If the data bus is 16 bits and the address bus is 32 bits, so the data is fetched in 2 x 16 bit groups.