Ch.6.3 Evaluating Your CPU and RAM

The Machine Cycle

The CPU is composed of two units: the control unit and the arithmetic logic unit (ALU). The control unit coordinates the activities of all the other computer components. The ALU performs all calculations and makes logic and comparison decisions for the computer. Every time the CPU performs a program instruction, it goes through the same series of steps, which are referred to as the machine cycle: 1. It fetches the required piece of data or instruction from RAM. 2. It decodes the instruction so the computer can understand it. 3. It executes the instruction. 4. It stores the results. It then starts the process over again.

How Much RAM Do You Need?

Because RAM is the temporary holding space for all the data and instructions that the computer uses while it is on, most computer users need quite a bit of RAM. The amount of RAM your system needs depends on how you use it. At a minimum, you need enough RAM to: Run the operating system and Run whatever software applications you're using.

Is Your CPU Fast Enough?

Even if your CPU meets the minimum requirements for a software program, if you're running other programs, you'll need to check to see how well the CPU is handling the entire load.

RAM Limit

Every computer is designed with a maximum limit on the amount of RAM it can support. In addition, the operating system running on that machine imposes its own limit. Once you know how much RAM your computer can support, you can determine the best configuration of memory modules to achieve the greatest amount of RAM.

If I buy the fastest processor, does that always ensure the best performance for my computer?

Not necessarily. A computer's overall performance depends on many other factors than just the processing speed.

What does the term "GHz" mean?

Processor speed is measured in gigahertz, or GHz, which refers to the number of machine cycles per second that the processor goes through. So, for example, a 3 GHz processor performs 3 billion machine cycles per second.

RAM Basics

RAM (random access memory) is the computer's temporary storage space. Although we refer to RAM as a form of storage, RAM is really the computer's short-term memory. RAM remembers everything that the computer needs to process data into information, but only while the computer is on. This means that RAM is an example of volatile storage. When the power is off, the data stored in RAM is cleared out. This is why, in addition to RAM, systems always include nonvolatile storage devices (such as hard disks) for permanent storage of instructions and data when the computer is powered off.

Adding RAM

RAM comes with installation instructions, which you should follow carefully. RAM is also relatively inexpensive compared with other system upgrade options. Still, the cost of RAM fluctuates in the marketplace as much as 400 percent over time, so if you're considering adding RAM, you should watch the prices of memory in online and print advertisements. Adding RAM to a personal computer is quite simple and relatively inexpensive. You simply line up the notches and push in the memory module. Just be sure that you're adding a memory module that's compatible with your computer.

Where Is RAM Located?

RAM is located on the motherboard. Memory modules (or memory cards) are the small circuit boards that hold a series of RAM chips. They fit into special slots on the motherboard. RAM capacity is measured in gigabytes (GB).

What is RAM? What kind of data is stored in RAM?

RAM is the computer's temporary storage space. Data stored in the RAM is volatile.

Where is the CPU located?

The CPU is located on the motherboard.

CPU Speed

The System window shows you which CPU is installed in your system as well as its speed. For example, the System window below shows that this computer has an Intel Core i5 running at 1.6 GHz.

How Much RAM Do You Have?

The amount of RAM that is actually sitting on memory modules in your computer is your computer's physical memory. As you can see here, this computer has 4 GB of RAM installed.

CPU Basics

The central processing unit (CPU or processor) is the "brains" of the computer. The computer's CPU carries out the following functions: It processes instructions. It performs calculations. It manages the flow of information through your computer system. It is responsible for processing the data you input into information.

How Much RAM Do You Need?

To determine how much RAM you need, list all the software applications you might be running at one time. For example, if you're running your operating system, word processing and spreadsheet programs, a web browser, a music player, and photo-editing software simultaneously, you would need a minimum of 9 GB of RAM. However, it's a good idea to have more than the minimum amount of RAM so you can use more programs in the future.

Memory Management

Windows uses a memory-management technique known as SuperFetch. SuperFetch monitors which applications you use the most and preloads these into your system memory so that they'll be ready to go. For example, if you have Word running, Windows stores as much of the information related to Word in RAM as it can, which speeds up how fast your application responds, because pulling information from RAM is so much faster than pulling it from the hard drive. You can watch this process at work using the Resource Monitor, which shows how the installed RAM is being used.

Is there a limit to how much RAM I can add to my computer?

Yes. Every computer is designed with a maximum limit on the amount of RAM it can support.

CPU Usage

You can tell whether your CPU speed is slowing down your system by watching how busy it is as you work on your computer. The percentage of time that your CPU is working is referred to as CPU usage. On Windows systems, Task Manager lets you access this data. The CPU Usage graph like the one shown here records your CPU usage for a certain amount of time. If you see that your CPU usage levels are over 90 percent during most of your work session, you may want to consider getting a faster, more powerful processor.

Replacing a CPU

motherboard If you choose to replace your CPU, you need to determine which CPU is compatible with your motherboard. In addition, because the CPU generates a lot of heat, a cooling device called a heat sink sits on top of the CPU to absorb heat. If you upgrade your CPU, you need to make sure you purchase the correct heat sink for your processor or make sure you purchase a kit that includes one. It can be fairly simple to replace a CPU: you line up the slots and drop it in. However, because it's important that you pick the right replacement part and process, many computer owners seek the help of professionals when upgrading their CPU.

Where Is the CPU?

motherboard The CPU is located on the motherboard, the primary circuit board of the computer system. There are several types on the market including Intel processors (such as the Core family with the i7, i5, i3, and the Centrino line) and AMD processors (like the Athlon and Phenom).