Choosing a Processor

The CPU (central processing unit) is the core of your computer. It's the large integrated circuit mounted in a socket on the motherboard that controls all of the computer's other components. All of the actual computing inside your computer takes place in the CPU, so the choice of a processor dictates the computer's performance level and can have a significant impact on its cost.

Both of the major CPU manufacturers, Intel and AMD, offer several families of processors with somewhat different designs and feature sets. Within each family, the price of a CPU chip increases along with its speed and performance. Therefore, it's necessary to choose a particular brand, family, and performance level when you shop for a new computer.

Or is it? One of the great secrets of the consumer computer business is that most people buy computers with much more processing power than they really need. For the vast majority of computer users, the real differences between CPUs may not matter very much.

Even a relatively slow processor can provide as much computing power as most of us are likely to need in a desktop or laptop computer (unless you plan to play cutting-edge video games or do large-scale graphic design). For high-volume network servers that are constantly sending and receiving files or messages, and for systems in multimedia entertainment centers and other processor-intensive applications, a faster and more powerful CPU can provide a noticeable improvement in performance.

One reason to buy a better CPU than you need right now is to anticipate the next round of upgrades to your hardware and software. A mid-range or better processor might be inexpensive insurance that protects your computer from becoming obsolete too soon. If you buy a new computer with the least expensive CPU, you might not be able to use it a year or two from now when you want to install the latest gotta-have-it enhancement to your system, such as a new operating system, a popular new game, or a program for editing digital photos or sound recordings.

Intel or AMD?

The two major manufacturers of CPU chips are Intel and AMD (Advanced Micro Devices). Both companies make excellent products. Both companies would tell you that they are dedicated to advancing the technology to make all of our lives more rewarding. Both work hard to meet those goals. The competition between the two keeps prices low and encourages them to develop even faster and better processors in order to preserve and expand their shares of the market.

It's not possible to use one brand as a direct replacement for the other. The physical form and some of the low-level features of Intel and AMD processors are not identical, so each processor requires a motherboard that was specifically designed to operate with that type of CPU. But the motherboards for both brands follow the same specifications for dimensions, electrical requirements, and for input and output connectors and signals, so it's entirely possible to build similar computers with either make of processor. Windows works equally well on either one. Unless you go out of your way to run a diagnostic measurement program, you might never notice any difference.

Processor speed

Extra speed makes a difference when your computer runs very large programs or processes large amounts of data, and benchmark programs that produce bar graphs like the one in Figure 3.1 can be impressive. If you run a daily or weekly report that examines hundreds of thousands of records and evaluates every transaction, a faster processor can complete the job more quickly. But the improvement is far less visible during routine home and office tasks like word processing and Web browsing.

Figure 3.1: Faster processors can produce impressive results in benchmark tests.

As their manufacturing processes improve and the technology advances, both AMD and Intel introduce newer and faster processors several times a year. When that happens, the prices of the previous speed demons drop, along with all the other members of the same processor family. And sometimes, the slowest version disappears from the list.

The difference in cost between the latest and greatest version of a CPU chip and a slower version that has been available for a year or two can be dramatic. A processor with a clock speed just 15 percent slower than the top-of-the-line version can reduce the cost of your computer by $200 or more. In most home and office settings, the apparent loss of performance is insignificant. On the other hand, buying the cheapest possible CPU is often false economy, because it may not have enough power for next year's new programs.

So the best strategy is usually to look for the best compromise between speed and cost, most often someplace close to the middle of the range. Unless you need to wring every possible bit of performance out of your computer, you probably don't need the fastest CPU.

The CPU's History of Speed

The speed and complexity of the CPU designs used in personal computers has grown almost unbelievably since Intel released the first microprocessor (the 4004) in 1971. Those early processor chips had a clock speed of 108 kHz (that's 108,000 cycles per second), and they contained the equivalent of 2,300 transistors. Today, the CPU inside a desktop computer might operate at 3 GHz (three billion cycles per second) or more and contain more than 200 million transistors. Moore's Law (named for its creator, Gordon Moore, one of the founders of Intel) predicts that the number of transistors within an integrated circuit of the same size will continue to double every 18 months, so you can expect the next generations of CPUs to be even faster and more complex than the ones that are available today.

Performance

Raw processing speed is not the only thing that contributes to a computer's performance. Other features of a CPU's internal design such as multiple processors and the amount of onboard cache memory can also help move data through the system more quickly. In some cases, those improved functions can compensate for a slower internal clock to produce faster overall performance.

Each processor family includes a different set of features. You can find detailed descriptions of each family and recommended processors for different uses at the Intel and AMD Web sites (http://www.intel.com/products and http://www.amd.com).