Fig 1.0 A Microchip that processes software/hardware instructions
The CPU is one of the main reasons for buying a computer. The faster the CPU can process instructions the faster the computer. However, this is not strictly true. An Intel Pentium 4 is faster than an Intel Pentium 3, in theory. And the "stripped down version" of the Intel Pentium 4 (the Celeron CPU) is supposed to be faster than the Intel Pentium 3. I say supposed and in theory because it depends how you slow the computer down or speed it up.
An Intel Pentium computer with a 7200 rpm hard drive is faster than an Intel Pentium computer with a 5400 rpm hard drive and Windows 10 with 4 GigaBytes of memory is faster than Windows 10 with only 1 GigaByte of memory. Also, a computer with an Intel 3.0 Ghz CPU will be faster than an a computer with an Intel 1.7 CPU inside it. So far this is as expected. However, you can have a computer with an AMD 1.7 Ghz CPU, 4GB of memory and a 7200 rpm hard drive that will out perform a computer with an Intel 3.0 Ghz CPU, 2GB of memory and a 5400rpm hard drive. This is because even though the AMD CPU processes instructions slower than the Intel Pentium CPU, its faster hard drive and extra 2GB of memory make it a lot quicker at moving files around.
If a Microsoft Word file on the hard drive for example is being copied into memory, perhaps for printing and/or editing purposes, the copying might be done at 1MB intervals whereas when Windows 10 knows it has more memory it knows it can copy data at 2MB intervals for example. And with a faster hard drive too moving files around, installing software, indexing files and so on also become faster. So the memory and hard drive make up for the slow CPU.
With time and progress manufacturers have now made it possible for the CPU to be split up into two or four parts (cores), known as Dual Core and Quad Core respectively, which basically means the CPU now has two or four brains to use. These core CPUs spread tasks among themselves, making it possible for one brain (core) to print out a document for example while another brain (core) takes care of processing internet tasks for example. These kind of CPUs are now common in all computers due to technology getting cheaper and so on. Therefore, to some degree, CPU speed is not so much of an issue these days in terms of computer speed.
Fig 1.1 Before buying a computer always check its CPU specs - If dual core, make sure each core is least 1.6 Ghz.
Saying the above; If you see a computer advertised as having a 3.0 Ghz Dual Core CPU it will more than likely have each core running at a speed of 1.5 Ghz each only and not at 3.0 Ghz each. Therefore, before buying a computer always check the speed of each core via the System Information control panel. In the above example my Dual Core computer has each core running at 1.60 Ghz; because it is a cheap computer.